With Celiacs you don't want her eating gluten at all. Not even an occasional Cheerio or cracker. Often, crumbs are enough to make someone with Celiacs sick. You need to check labels carefully and make sure the school is aware about what to look for and how to avoid cross contamination.

I suggest you let the school know about the diagnosis and see what steps they are going to take. We had luck with our preschool making homemade playdough for the classroom rather then the store brand which contains wheat/gluten. You can also provide snacks that are comparable to what kids are having. And if they are decorating cookies - send in a gluten free cookie for her to decorate and eat.

My DS is allergic to dairy, soy, and eggs, which eliminates pretty much any food provided at our daycare except for fresh fruit. I do what I can to provide a snack or treat that is similar to what everyone else is eating. I know it seems like a daunting task right now, but it does get a lot easier.
Echoing what PP have said - make sure the teachers know what your child can and cannot eat (if food is provided) and to let you know in advance about any "special" food days. They have a container of safe snacks in our DS room at school and we refill it as needed. I can usually provide a safe alternative for special days (safe cookies and frosting to decorate, safe graham crackers for gingerbread houses, etc), but we have had a few hiccups along the way.
No one wants their kid to be left out if at all possible, but with food allergies there may be times when it happens.
In social situations (birthday parties, other events), I usually call and ask what food they're serving so I can supplement if needed. I keep safe cupcakes in the freezer at all times so I just have to defrost one. I also usually have pizza (homemade and individually wrapped) in the freezer as well. The only thing I'm dreading are the spur of the moment "let's go get ice cream!" suggestions (already happened once, but DS wasn't paying attention). I also keep a few safe snacks in the car for when we go out.
I highly recommend the Kids with Food Allergies site and forums.

My child has gluten intolerance and a bunch of allergies. Here are some tips:

-Let the teacher know and request that the school not give your child any food you have not provided. Also, research the apple juice they use. There are actually applejuices made with gluten!Provide teacher with a bunch of allergy safe treats. Ask if teacher would be kind enough to let you know in advance about cupcake celebrations. Udi's makes some great GF chocolate muffins we often used as substitutes for cupcakes if I didn't have any in the freezer. Also, the teacher could just keep 1 or 2 in the freezer for impromptu celebrations.

-Request that your child do a different activity during cooking or ask if they could do it on a day your child isn't there. One teacher had Celiac so all the baking was gluten free.

-Order or make your own gluten free playdough.

You might also find this thread helpful. Not sure if there are repeat suggestions, but sometimes it's just nice to go out:

http://www.dcurbanmom.com/jforum/posts/list/303166.page#3512870

OP here. Thank you all for the responses. And 21:12 - yes that was me. The ideas in that thread were great, and although we're not all the way there, the general diet / creating a GF home is feeling at least somewhat manageable now. It's just this new realization that there are all these other environments where we have to deal with this now. Like how the activity at tonight's kid event involved making a turtle out of a cracker and other food products. (She really wanted to make it so I let her, and just made sure she washed her hands well afterwards.)

And 21:46 - thank you for the advice. I do think her preschool will be willing to work with me, but it's a small co-op preschool, so I'm just not sure they have much experience with something like celiac. So we'll work on it, and it's really only for the next month or so as she starts kindergarten in the fall.

My child was diagnosed right before starting preschool. I would not let my 3 yo touch gluten at first because its hard for kids to keep their hands out of their mouths. I also didn't let her touch play dough unless I made it myself - I didn't trust the other parents to use rice flour when making it either. I worked with the school to eliminate all gluten from classroom supplies and craft activities. Our preschool didn't do baking and we avoid cooking birthday parties and activities. We keep some emergency birthday treats at school, and send in a cupcake for birthdays. We bring pizza and cake and GF chips to birthday parties.

You should be able to provide substitutes for crafts if given notice. If the teacher won't work with you to keep your child healthy, and this could be covered by IEP/ADA rules if necessary, then I would look for a new preschool. I went absolutely strict after diagnosis. Now my child is able to manage social situation herself and knows there is not any wiggle room. If she wants to have "just a bite" when she is an adult I can't stop her but when she is little her health is my responsibility.

My DC (non school age) has a wheat allergy. It hasn't been a problem except for getting family to take it seriously. Some of the grandparents are a bit old school and aren't used to food allergies. My MIL in particular has a hard time understanding that things like pasta and couscous are WHEAT products so we have to watch her like a hawk and feel uncomfortable leaving our child with MIL for long periods of time.

We haven't done the classroom thing yet but one tip for dealing with restaurants: make sure that you stress to the waitstaff that you have a medical condition that makes it so you must be GF...a lot of people are doing it for the trend diet now and so restaurants can kind of roll their eyes and take it not very seriously. I have been out with a Celiac friend and seen her send back two plates at a well known restaurant because actually, there was gluten in there after all.

OP,

Make sure your school knows about cross contamination. Basically anything with gluten in it would be treated like it was raw meat with any surfaces it comes into contact with. They need to make sure that your DD's place is wiped clean b/f she eats.

Also, don't know if this was you, but there was some good suggestions for food here:
http://www.dcurbanmom.com/jforum/posts/list/300008.page

GF is fairly easy to do once you get the hang of it. We've had many a GF b-day party.

With celiac I'd be strict with what she eats.

Handling gluten items isn't ideal b/c residue can easily transfer to her mouth. Fortunately there are lots of gf options and even gf playdough.

Is her preschool willing to work with you on this? Also, she'll need to learn not to accept food that hasn't been vetted first.

I apologize if this is the wrong forum to post, as my child is NT and I know in the big scheme of things that these issues are relatively minor.

But we recently received a celiac diagnosis, and beyond the expected issues of transitioning to a gluten free diet, I'm starting to struggle with how this plays out in social / school settings. Like today when my kid didn't want to go to preschool because the cooking activity was decorating cookies and another activity involved goldfish crackers. We're also just starting on this, so I'm not sure how sensitive she is / how strict I need to be with her and how much I need to push the school (i.e. if she can handle goldfish at all, etc.)

Not sure I really have a question as much as I'm looking for advice from BTDT parents as to how best to manage this new reality, and how to keep my child both physically and emotionally healthy. So thank you in advance for your patience with me, and for any advice.