be careful with smoked salmon; sometimes it's not gluten free b/c they add coloring. I would definitely look for something that's marked GF on the label.
Thomas' bagels are vegan (but obviously not GF:
http://www.peta.org/living/vegetarian-living/accidentally-vegan.aspx
If you want to search for a recipe that meets both criteria, I like this site:
http://www.mealsforyou.com/cgi-bin/advancedSearch
P.S. It's very kind of you to be so considerate of your guests.