We did a princess party for DD for her 4th. We had tutus and capes as favors. Just be sure that you have extras-all the girls wanted a cape and several of the boys wore tutus.

My son's favorite thing to do is dress up in his knight or king costume. And I agree with the PP -- he's had hurt feelings when some of his favorite girl friends have had princess or other girly parties and not invited him. I'm sad at some of the gender division that's starting now that he's 4.

op here, thanks everyone for the nice responses and many cute ideas

My DD went to one. The invite said kids could dress up if they wanted to and when we went, kids were dressed up as everything. The girls were princesses, and the boys had swords, were ninja turtles, spiderman, etc. The kids all seemed to have a lot of fun. They hired a princess actress, who handed our prizes like princess rings and tiaras. Some of the boys were into it and some were off swordfighting. This was for a 3 year old party.