Your son is going to love it no matter what you do! Adding a border and just using a whole piece in the center would look quite nice when it was machine quilted. Other methods depend on how much experience you have. All the suggestions are possible.
I made a quilt similar to this for my son-in-law once while visiting them ...in a hurry, didn't have many supplies on hand ...so just used the wild life fabric and backed with fleece, no batting, etc. Then I made a pillow to match. It is now 17 years later and he is still dragging that around to nap with on the couch or in his chair.