Have you tried using cocunut milk and split red lentils as a base for a mild curry/dahl? My toddler ds (who is also rather picky) loves it - creamy and sweet I suppose. I make it either with lots of chopped veg (onions, leeks, carrots, courgettes, peas - anything really!) or with veg and chicken, and I add a small amount of tumeric, cumin and cinnamon. It freezes well in batches, and we all like it, so makes a family meal.
He also loves home-made chicken and apple burgers and sausage casserole made with passata, chickpeas, aubergines, peppers and courgettes (which again both freeze well). Any good?