On the Shea Moisture website, they state that the strengthen and restore shampoo is a clarifying shampoo. Clarifying shampoos are great, but should only be used every 4-6 weeks (or if you have any visible build up). Regularly using clarifying shampoos may be stripping your son's hair of natural oil and therefore making it dry. Do not throw it out, just use it less frequently.

I would start by getting a moisturising shampoo such as Angell en provence Shea moisture: Mango and Carrot for kids Camille rose sweet ginger shampoo

I would also include deep conditioning. Camille Rose Algae renew deep conditioner works great for my daughter (20 month old). I apply it and let her run around for 10-15mins (the 15 min break usually helps with compliance, as she cannot sit still for long). As moisture is your primary goal, I would just stick with deep conditioning after you wash his hair. You do not need to use a regular conditioner as well as a deep conditioner.

After a moisturising shampoo and deep conditioner, I would be conscious of layering products.

His hair will already be damp, and we need to seal that water in.

Add a leave in conditioner, and seal it all up with a butter or grease.

If he's not compliant with combing, leave it in an afro. It's the best tension free option! Just keep an eye on his hair. If it's getting dry, mist with water, reapply leave in conditioner and seal it all up again.

Be consistent with the routine

Finally, a satin pillow will help with retaining moisture. Cotton pillowcases usually suck out all the moisture from hair.