Genuine question, why is it such an issue if their kids helped?
dd1 is 10, she is a good cook, she will be baking shortbread for her teacher. She does homemade stuff for Grandparents every year.
dd2 is 7 she is also a good cook, and made sweets for family last year.
Both girls know perfectly well how to wash their hands etc, and have done since tiny.
Besides which, anything properly cooked is well, cooked, so even if there was bacteria in the first place, it is now dead!
My biggest issue is shelf life. Too much food at Christmas.
I also don't do any soaps/bath smellies due to sensitive skin, so whether bought or made it is no good.
I think it works best for specific people when you know their taste.