Honesty box at playgroup

Hi, I'm hoping to gauge some opinions regarding a new pre-schooler roleplay session I'm in the process of setting up.  It will run like a traditional playgroup with parents staying and I'd like to sell drinks and snacks.  I would like it to be casual and friendly where parents can make their own drinks and buy what they like by self service and trusting them to put the correct money in the honesty box.  Do you think I'm mad?!!  I will obviously be there to facilitate, but would rather interact with the children than play waitress.  What do you think?  Thanks for you time x