Which kid doesn’t like a good burger? Make your burgers from better, healthier cuts of meat like shoulder steak, or tenderloin. Mix beef with veal when making burgers. Grill chicken on the BBQ, it is hard to resist. Throw vegetables even corn on the grill as well.
Try cooking meats and fish differently to make it interesting. If you are used to well done steak or meat, then cook it rare and juicy. Cook it in a sweet marinade or hot sauce if they like spice.
Fish sticks can be warmed up with some cheddar cheese on top. Tuna fish can be mixed into macaroni and cheese. Eggs are a good source of protein and you can cook them up in many different ways.
Try offering them bites from your own plate and not giving them a plate of their own. If they refuse to try things then use their logic. When they want to do something like watch a NEW video or game, you say “I don’t like that, I only like what I like and what I know. I don’t want to try anything new” If they want to go to a new store or new park “I don’t like that place, its new I only like what I like and I don’t want to try anything new”. They will get the message. In most cases it has nothing to do with what they like or dislike it is just a matter of being stubborn and not wanting to make changes.