New Project in the Works...Need Some Ideas

I am working on an idea for Portrait Parties.  The idea is that I offer one mom a free package (8x10, 2 5x7s, and some wallets, maybe.)  She invites 5 kiddos over for a  Portrait Party playdate.  I will set up a spot and take one or two poses for each child in the group, and maybe one of them all together.  I will mail a proof out to the moms the next week, and they can order any prints they would like to have.  Then, hopefully,  at least one of the moms from the playdate will have her own party and invite 5 other friends, and so on.  So far, I have two ideas for set ups.  One involving a fish bowl, and one with feet and names.  Does anyone have any thoughts on another "theme?"  It wouldn't be much fun to have 2 portraits from the same scene if you decided to host your own party...
Would you rather have it at your home, or somewhere else?  What time of day would be best? Is 5 a good number of kids? What activities would you plan to keep everyone busy when it was just play time? Any other ideas?
Also, if anyone reading this would like to volunteer for a guinea-pig session, please let me know!!