Eggs! Eggs are brilliant. Scrambled (and mixed with milk)- protein, calcium and lots of other vitamins, dippy eggs and soldiers are always excellent and easy breakfasts/dinner even! Make the switch from white bread to 50/50 and eventually to wholemeal. Use a fortified spread on the bread. Cheesy omelettes are always good too. I lurve eggs.
Fruit wise. Make a fruit pizza? It's very simple. You can get recipes on google for the base, the sauce can be yogurt and then just top with a shed load of fruit. Banana muffins/bread/cookies are always good and you can make a batch to freeze. Blueberry muffins too. Pancakes for breakfast topped with yogurt and fruit. Greek yogurt mixed with honey/maple syrup and peanut butter and put some berries/grapes in there? Make shapes out of the fruit. Sometimes I do rice cakes topped with peanut butter, banana ears and eyes and blueberry mouth- rice cake bear.
Easy teas- as others have said homemade pizza is always good. Use wholemeal breakfast muffins, tortillas or even pitta breads as the base. Let the DC top with what they choose (within reason of course). Fish fingers are fine, especially the omega 3 Birdseye ones. Sweet potato chips? Just chop sweet potatoes into wedges, spray with some olive oil and into the oven they go. Fajitas are usually a hit with DC. Picnic tea or 'higgeldy piggeldy tea' as I call it always goes down well. Selection of carrot sticks, pepper sticks, ham slices, cheese, hummus, fruit etc. Pasta is never not good. Tuna pasta, cheesy pasta, pasta mixed with quorn or chicken pieces. Shepherds pie when weather gets cooler, hide some thinly chopped veggies in there. Beans on toast with cheese on top is one of the easiest and best meals you can have. Switch to low salt/sugar beans, 50/50 and then eventually wholemeal bread, fortified spread on the bread and top the beans with grated cheese. There's just about everything going on with that meal- calcium, protein, iron, carbs, good fats. Linda McCartney sausages, jacket potatoes. Cheesy bean mash.
Squash wise slowly weaken the squash. To jazz water up add strawberry pieces or squeeze some orange/lemon in there. Offer milk twice a day- flavoured milk
Breakfast wise toast is fine, try topping with peanut butter instead of chocolate spread. Cereals- porridge topped with honey/maple syrup/peanut butter/mix some yogurt in there, mash a banana in with it and top with chopped berries (make a face with the berries). Weetabix is good. Pancakes for a treat- use a sugar free recipe and top with honey or yogurt to sweeten.