You can have him apply coconut oil as a natural moisturizer. Put it on and comb it through. Let it sit for 30 minutes and then rinse it out. This will help heal the hair and moisturize it. You don't want to use a lot of products on hair that is frizzy as it will just worsen the condition. Use natural shampoos and don't shampoo every day. Most people shampoo their hair with harsh shampoos way too often, stripping the natural oils and leading to breakage and frizz.
To keep it down when leaving the house etc. just rub a bit of olive or coconut oil on the palms of the hands and kind of smooth the hair down. Just a tiny bit or it will make his hair look greasy.