My son turned 3 in December so we had a snowman party.
The invitations were made with stamps that he helped decorate. For the party we had entertainment stations the kids and parents could go to as they wished. This helped break up the crowd and allowed each child to pick what they wanted to do. We had a pack and play filled with snow (packing peanuts) for the kids to play in, we had pin the accessories on the snowman including the body, arms, hat, eyes, nose, etc, we had a craft station which made a snowman art project with cotton balls and fake snow, and had frosty the snowman movie playing. It was a blast.
