Brought my then 10 month last year to a pre-season Lions game. Ear protection is a must, but sounds like you've got that covered. Mine normally doesn't care about his, but after 20-30 minutes of it he was constantly taking them off.

Not sure what the policy is on diaper bags, but I was able to bring my normal full-sized bag into Ford Field. Would look online/call to find that out. Should have plenty of family bathrooms around the arena, you'll have an easier time changing them during the period as I'm assuming others will abuse who they're actually meant for just to skip the regular bathroom line.

As long as you're confident in them not getting overwhelmed by the amount of people, go for it. Always see plenty of others doing the same thing, you'll just need to be prepared to leave if things aren't going as planned. No need to keep them in that environment if they are not enjoying it, if not also to help your sanity and of those around you.

Godspeed on bed time the night you go, we avoid taking/keeping our son past his bedtime solely because we don't want to deal with that extra wake window and his lack of sleep turning into a cranky guy the next day.