The references to gridiron are very annoying, though I suppose you need them. It would be much better if the Muggle sport they're playing was actually an interesting one, like football, rugby, or baseball.
Author's response
Your forgetting: to me it/is/ football. It's violent, bloody, and a whole lot of fun to charge at someone and hit them when you're both going full tilt.
I make jokes about it too, and I only refer to it sparingly.
As for your list of 'interesting' sports, soccer is actually the most popular sport in America...amongst people under the age of 14. Rugby is a slower, less violent precursor to American football, and baseball is, as my dad says, like watching paint dry.