The girls were pretty excited about this. At first they weren't sure what to do, but when I explained they could do whatever they wanted they went right to it.
They worked and worked, and then decided they needed sprinkles. I gave them a few and they came back in a little while later for chocolate chips, which I gave them. Through this process I ended up giving them more flour, water, and finally a banana to add to their cake. This is not something I'd do every day because you can imagine the clean up was a bit involved, but they had fun, and stayed outside for a long time 'baking'.
Cake is served!