I think I would do the simple blocks like in the picture and use a double bat of cotton (bottom) and then wool with maybe a flannel or nice muslin backing. The double bat will be heavy enough for him and plenty warm too.
I'd use the long arm to tack it down and then tie it. I've tied 2 t-shirt quilts and it can be a bit of a pain---have a pair of needle nose pliers to pull that needle if it get's stuck.
Or you could just machine quilt a grid pattern and then tie about center of your blocks (or every other if 6" of smaller) and it would be that tied quilt but also have a machine grid stand up to the washing and give you an easier quilt to tie with.