S.D.
You could have a big sandbox with prizes hidden in the sand that they dig out. Pin the tail on something? Pinata? They have those kind of pinatas now where the kids pull the strings out vs. hitting it with a bat or something.
Have you already sent out the invitations? You could ask all the children to come in their PJs and have like a pretend Slumber Party theme. Popcorn, read a story to them, do a craft,and they could each take a stuffed animal home with them for their "goodie"?