The Walmart material will not hold up. Take it from someone who did make a quilt with that material. If you want it to last, then you better quit now and get better fabric.
I have done the same, started a quilt and quit because did not like, that is another reason I have several UFOs. I would use what you have for a simple couch throw, be sure to quilt it heavily so you do get some durability into it, then move onto better fabrics for your son. To me, nothing would be more disappointing than to receive a quilt and it not last for a long time. We like heirlooms and quilts are one of those heirlooms we like to keep.