I love the blanket cape idea, and I think the suggestions above are good on tagging for children.
I think adults will like them too, for watching t.v., or for outdoor spectator sports that might get a little cool at certain times of the year. If you wanted to try a sampling using the colors/logos of a few popular NFL teams, I think you might see a great response in adult purchases. Matching adult & child "superhero" sets might do well also, encouraging adults to be active in their child's playtime. Tags might be playtime, sports, outdoors, cool weather, t.v., etc.
Good luck!