You can probably start by switching out some unhealthy snack food such as chips and cookies and things like that. Kids LOVE to have sugar, so maybe try buying some healthy fruits for him to have. And i don't know how willing your son is to try foods, but try buying more than just apples and bananas. You can try mangos, plums, pineapple, etc. Switching out those really unhealthy processed foods for some natural fruit can also help him overall feel a lot more active and happier
For your meals, especially with dinner, maybe try to have salad as a side dish to your meal. And Im also not sure on your serving sizes, but especially for rice, a healthy serving size will be about the size of your fist. Since you say you make a lot of soups (again im not sure the contents) you can try to make your own homemade soups. That way you can control the amount of sodium added in. You can also add more vegetables such as carrots or celery.
If that doesnt work, try to take him grocery shopping with you. Have him pick out what fruits and veggies he would like to eat. The fresher the better. Try to avoid most canned fruit since they tend to have more added sugar.