First of all, if you're in Dallas (or San Diego) you can rent a lens for the day for 40 dollars. Check the camera shops online for those areas. I'd highly recommend the 100-400 zoom lens. It's an L series and white, and it's the only 100-400 Canon makes. It's good for what you're doing.
Except for light. The lens needs a lot of light.
You could also rent, for about the same price, a 300 L series.
Unfortunately, the stadium is probably going to be a PIA about equipment.
If I were you, I'd bring the camera with kit lens. You won't be getting any really great action shots of the game (unless you can get a little closer....and even then you won't get great up close action shots), but you'll get great pictures of the stadium and the fans. Who knows what you'll see.
I'd definitely bring my camera if I were there.
PS. I'm a Charger's fan as well. Always have been since I was born and raised in Encinitas, CA (North County, San Diego). Also my mom dated Dan Fouts for a while, which I thought was pretty cool at the time. Beating Dallas won't be easy, but the Chargers just won their seventh game in a row and are now 9-3 I believe. Not bad.
Thank you. 