Generally children will not starve themselves. If you make good food available and limit unhealthy snacks, eventually they will eat. Cut up fruit for snacks, removing cores and pits, etc., and present it on a platter. Fruit kebabs are one creative idea. Think about the texture.
Children often prefer raw to cooked vegetables, because they dislike slimy and squishy as textures.
Keep foods separate from each other on the plate. Add beans to spaghetti sauce. Add shredded carrots to a tuna or chicken salad sandwich mixture. Add shredded or pureed fruit to muffins or pancakes. Tofu blends well into lots of things, like scrambled eggs, for example.