I stopped selling at mom to mom sales years ago because there was no demand for older children’s clothing, NO TIME, too expensive-not worth my time, and the organizers really did not know what they were doing (no advertisement, organize, etc.) One sale I was selling at demanded all sellers bring in baked sale items (like we have time to bake or buy items when we were organizing our own items to sell!) And another time I had to drang in my own tables from the custodians area due to the organizer did not have everything organized and ready for seller to set up (and the kicker was I had a tiny table for 18 bins full of clothing-when I paid for 2 20ft tables.)
I have had better luck on craigslist, yard sales, and the mom2mom list website. They have a forums section that you will be able to place free ads and chat too!
http://www.mom2momlist.com/