Commercially made snack bars made from oats and fruit can go down well (Organix, Ella's Kitchen) as can the dried fruit children's snacks (Bear nibbles - fruit yoyos, paws, claws). Organix also does Banana & Date bars, Apple & Date bars.
You can then try making your own versions at home. Flapjacks made with dairy free spread instead of butter, with dried fruit added such as raisins, cranberries, apricots.
Main meals:
Spag bol.
Roast chicken with veg. Some children can be very fussy about the chicken... try with skin on, skin off, roasted vs fried vs fried in a pan with a lid on which helps keep it more white colour.
Sausage rolls - shortcrust pastry made with dairy free spread.
Risotto - all sorts of things can be added to that. Keep it simple at first.
Fish - sea bass / salmon, with veg. Can be a bit costly so experiment with different types of fish to find which ones they like and fit your budget.
Biscuits can be made with dairy free spread - I use the Mumsnet 321 biscuit recipe and have used it for a child who was diary free (used Vitalite), wheat free, gluten free (used Dove wheat/gluten free flour).
Can they have Coconut milk based products? The Coconut Cooperative does coconut milk based yogurts.
Children do tend to eat the same things a lot of the time so I would not overly worry about the lack of variety. I would though encourage trying different vegetables (cucumber, broccoli, carrot, sweetcorn, sweet potato, peas, peppers, mushrooms, potato tend to be toddler acceptable... some things they may have raw - 2yr old I care for loves raw mushrooms not cooked). Also a variety of fruit - as we get more into Winter you could try stewed fruit, such a apples (Bramley apples cut up and put in a saucepan with as little water as possible). Baked apple. Mumsnet Food/Recipes forum has lots of Apple ideas posted over the last decade or so - Google: mumsnet stewed apples