Firstly, I love the way you are being so thoughtful about him!
Yeah, I guess you've understood that your recipe idea is very not suitable for someone watching their weight and general health.
Best thing is to ask him what he likes to eat, what will suit his dietary needs, and what would be easy for him to cook, eat and digest when he gets home from surgery- rather than just making up ideas of your own, made from high fat ingredients.
So he may welcome some healthy main course dishes that can be made and frozen in individual portions rather than the tray size you have described that would feed 4-6. I.e. some things he can quickly microwave for himself if he is tired and doesn't want too much fuss and prep. I often make such things for elderly relatives and neighbours ( he isn't elderly but may be feeling a bit below par and want easy healthy tasty stuff)- eg. home-made chicken noodle soup, veg pasta/rice bake, chilli or curry if he likes spicy food.
And I think he may very well fancy something sweet like a tray of brownies or lemon drizzle cake.
Remember to get some nice fruit for him too- fresh or frozen, can be made into smoothies or chopped into a bowl of muesli.
Check he has the basics like milk and bread.