JusRol croissants/pain au chocolat/cinnamon rolls in a tube to bake for breakfast (or go to Parc Market for fresh croissants/bread)
Nice OJ
Decent coffee (and teabags), sachets of hot chocolate
Jar of favourite jam/marmalade/preserve (possibly Nutella also for DCs)
Their favourite cereal
I always bring a tin of tuna and tin of sweetcorn to make tuna mic for a salad or tuna melts, or to use in a stir fried rice or pasta dish
Old El Paso do lovely easy kits for fajitas, tacos or quesedillas
A bag of pasta, pack of bacon lardons, pack of musrooms and a jar of pesto rossa is another simple and tasty dinner
Bag of rice, nice jar of curry sauce (or a tub of fresh curry sauce from chilled aisle), meat/fish, maybe some veg to add, and a pack of ready cooked puppodums or naan breads, chop a couple of tomatoes and a spring onion up together and season with freshly ground black pepper as a side dish
small jar of mayonnaise and small bottle of ketchup are essentials with DCs
And bring some dishwasher tablets from home if you can, as you don't want to washup much (I also bring a 100ml travel bottle filled with washup liquid for the little washup we need to do, pots etc, and that is plenty for a week - we eat in most meals). I have a pair of glass salt and pepper which have grinders in their lids (supermarket version) that I keep for self catering holidays, and a pack of coffee filters from various trips in case is it a filter machine.
And snacky stuff - cooked meat, cherry tomatoes, carrots and peppers (to cut into sticks), hummus and breadsticks, pesto, olives, cheese (we like a selection of cheese to slice but I also bring a bag of grated mozzarella or cheddar for sprinkling on pasta or making melts for lunches), roasted peanuts and crisps, some biscuits, lots of fruit, salad stuff etc.
Squash, fizzy water, gin, tonic, wine/beer
milk, butter (real butter is good to use to cook with as well if you don't want to bring a small bottle of olive oil, but olive oil also useful for salad dressings),
eggs are great for all sorts - use with some cream to make a sauce for pasta carbonara, or a Spanish omlette with meat (bacon or chicken is good) and veg (onion, mushroom, peppers, tomato) and cheese in it, not just boiled or fried or scrambled for breakfast/lunch