You OWN that child 24/7 365 1/4 days a year.  Channel all your preferences to all of their caretakers -- all the time.  Not just 98% of your rules, 100% of your rules.  Cover everything.   Anyone who's in your house, on your property, inside the emanations of your chakra needs to follow the rules.  Not just "he's allergic to peanuts and eggs" .   If you don't want him nibbling on grandpa's ham sandwich, make that point;  only organic, then make that point;  no products that you are boycotting, make that point emphatically.  If the caretakers don't respond , don't be surprised.  Nodding and trancing out at the same time is the universally recommended response to Daughter [in-law] Model 0.1.