Thank you to all of you for your suggestions. They are great.
Unfortunately I don't think I'm going to make the quilt after all. We were at my daughter's and grandson's last night. It seems his other grandmother just bought him a new comforter for his bed. So it's highly unlikely they'd take it off to put a quilt on, especially for winter.
Plus I was considering using spiderman fabric for the majority of it. And am having second thoughts as to whether that would just be too much superheros and how long would he like it.
This keeps happening. I was all but on my way to the store to get the supplies for his Halloween Costume when I found out the other grandma had bought him one from the Disney Store. How can you compete with that?