I would like to put out toothpicks with marshmallows and gumdrops for children to use to build towers. This was always a fun activity when I was a child and I don't think very many of our visitors will have done this before.
(Plus, it is always fun to throw a simple math activity in since I teach math.)
I would like to hand out THIS tutorial from Raising Olives on how to make a marshmallow gun as well. How fun! Too bad it isn't practical for a large group of kids.