Wow! That is such a wonderful quilt! It really captures the essence of a 16yo young man. After seeing your entire quilting pattern, I really think that is enough quilting. I wouldn't add more. When you present the quilt to the family, I would give them instructions on how to treat it gently. It can be used to drape over a couch, wrap up in, even make forts with, but they wouldn't want to routinely sit on it. Washer should not have a central agitator, wash cycle should be short with cool water, and remove from dryer before completely dry. Never hang wet on a clothesline. And return it to you for repairs right away if they should see a seam coming apart or other problem. Earlier repair is much easier and better for the quilt.
Honestly, though, I think the quilt will be fine as is. What a wonderful gift to the family!