Yes that does not sound like a very 'committed' to being vegetarian family at least for the 'child' ... however I have had clients where the mother was a total vegan by choice including not wearing clothes or footwear and so forth made from animals however respected both her husband and her children's right to choose their own moral compass around consuming animals or animal byproducts ~ so dad and the kids ate meat when dad was the one cooking dinner and they were allowed to eat meat here.

I agree with Cfred that IME cooking vegetarian is really quite easy ... we have a 'vegetarian' meal at least once a week here with a protein being served that is not 'meat/animal' related such as tofu stir fry or legumes in a soup/stew/chili or what not.

I currently have a child with Celiac and two children with a dairy allergy and I accommodate both without challenge and everyone able to eat the same meal so I am not dealing with a 'why does Johnny get to have X while we are having Y' debates ~ takes some creative thinking sometimes for sure but not too much challenge.

For example I still make my 'homemade mac and cheese' for them but use gluten free quinoa pasta or brown rice pasta and I replaced the milk with almond milk, butter with the Earth's Best and cheese with a non cow's milk source... just do not buy that Dalya brand cheese replacement it tastes like ASS but there are some vegan cheeses out there that are actually not too bad and melt nice and creamy ... fortunately both my little dudes are ok with 'goats milk cheese' at the moment so I can use that thankfully and in the past when it was only 1 child with the allergy what I have done is just taken the dairy allergy child's noodles and put them aside and tossed them with the Earths Balance butter replacement and than topped with some of the more expensive 'cheese substitute' grated on top and made everyone else the normal mac and cheese recipe.

I think meal prep for a group while accommodating food allergies is like everything in life it you just need to be motivated to want to do it and than it just takes practice to get a groove that works for ya ~ my last centre I worked at made all their own baby food in the kitchen and on top of that 'accommodated' food allergies / restrictions as long as they were not 'anaphylaxis'. So when I use to cover to cook in the kitchen you could be dealing with cooking for 20 infants in varying stages of 'adjusting to table food' plus up to another 20 children's varying food allergies and restrictions needing substitutions out of 100 or so children you were cooking for so I kinda got a groove for the 'group cooking' while checking that everyone's dietary needs were met ... so now doing it for 1 or 2 kids out of only 5 seems like a piece of cake!