Eeeeh I'm rather lazy, so all I'm gonna say is that in the Lolita Handbook on LJ (the link is in the "Quick Lolita Handbook" stickied in this forum) has a section devoted to "loli activities" that you may indulge yourself in :3
Some of the ideas are rather...creative? XD There's no way you'd catch me in loli at an ice rink since I can't skate :P But other than that, it has really good ideas as to what to do for loli activities.
But if you're going to host it at a con...Well, good luck trying to work that out XD I know for Anime Central (hosted in Illinois annually) we're not allowed to have foods/drinks (besides water) in the convention rooms so no tea party there :\
Anyway, if you figure something that's not already listed as a "loli activity" in the Lolita Handbook on LJ, let me know! I'm interested in new ideas :3