Baking experiments or “science” experiments… always ends up the same: disastrous mess.
I don’t want to discourage them from doing something that is fun, but wow… so much work to clean up after that.
I know how you feel!
The best thing to do in my opinion is require that they are in charge of cleanup for all “experiments”. If they can’t clean up, then they can’t experiment.
My 10 year old loves cooking so we bought her a easy bake oven and that helped a lot and we make her clean up afterwards.