As a gift to S's primary friends (and two cousins), we hosted a cookie party a few days before Christmas. This also turned into a small offering for parents... two hours minus a three year old to tackle last minute holiday errands. I hope we can make it a tradition.
The kids decorated/piled-stuff-on sugar cookies. Amazing how quickly the sugar kicked in. Potent stuff.
We moved to the kitchen, where the kids each took a turn adding an ingredient to the mixer for chocolate chip cookies that baked while they played. There were a few "samples." Don't worry -- I kept the sanitizer handy.