A couple of friends and I are starting a play groups for our kids (ages 13 months - 30 months). We want to make it purely an opportunity for them to have fun, and learn social skills in dealing with children older and younger than themselves. Could you give us some suggestions of activities that are age appropriate and how much structure the play group should have?
A playgroup such as you described can be a wonderful opportunity for mothers to get together on a regular basis and for the children to start to become familiar with one another. But they're on the young side to be playing with one another—up to the age of three they tend to play next to each other, rather than engage in the imaginative play of older children. And because the power of imitation is so strong in the young child, whatever they see another child doing or playing with, they immediately want the same thing! We can interpret this as their need to learn social skills, but it's a tricky age because they aren't yet old enough to understand sharing or being able to wait. So don't expect play to go smoothly, and remember to model the behavior you want ("We need to share with our friends") rather than swooping down with admonitions such as "Don't grab!"
Outside free play can work well at a park or in a yard, but if your weather is too cold, I might suggest some kind of mom-tot activity rather than just letting the children play at someone's house. Activities that work well might include cutting out cookies or kneading bread, then doing a little singing circle with some finger plays or movements, and then having snack together. Having it at the same person's house each time and sticking to a rhythm that works (once you find one) would also help the children to grow into the time by knowing what to expect. Although it's really possible to keep it simple and free form and get together at the park or in someone's home, if you want to create something with more structure, there are some good suggestions in the book by Sarah Baldwin, Nurturing Children and Families: One Model of a Parent/Child Program in a Waldorf School. It's available from www.waldorfearlychildhood.com.