We gathered all of the ingredients, and I halved the recipe I found on about.com.
She did the halving all by herself in her head when I told her the measurements out loud. It was great! Learning math and science at the same time.
She played around with it for awhile, adding different colours until she was satisfied that it looked like bloodied body parts.
I'll bet they can come up with great ideas on how to use it, and get messy while having fun.