When grandparents want to cook
Tell them the food your child already eats, and any allergy, before they shop. A loving cook still needs that list.

Before they shop
Ask for the familiar food on the plate beside anything new. Praise the cook for that, not for getting your child to finish.
“Rice, and no milk, so no cheese or yogurt” prevents a loving mistake. Say it early.
The diet in one sentence
Vegetarian is “no egg, meat, or fish.” Includes egg is “egg is fine, meat is not.” Includes meat is the plate that can hold chicken.
Grandparents do not have to memorise a philosophy. They need the sentence and one food that always works.
If they already cooked the wrong thing
Thank them, and serve the child the safe familiar food you brought or can find. A hurt feeling can be repaired. An allergy cannot be negotiated at the table.
Do not let “just a taste” override an allergy. This page cannot clear a food.
A sentence you can say
“Rice on the plate is the help we needed. Thank you.”