Make sure you get the full pit/paddock pass along with the Garage Pass. It's like $50 just for an 'infield pass' and damn - that's a ton of walking.
You could also write to Jeff Gordon on his behalf and explain the situation to him - you might just wind up getting invited to be one of his 'guests' at the track. Now wouldn't that be cool. The drivers are really cool about 'special interest' fans... good PR for them, plus the fan gets some time with their favorite driver too. Look into it.
I know the tickets I got last year were pretty good seats, and they ran me $400 for the pair since I didn't know I was going to be in Dallas anyway until about a month before the race.
Also check into getting special access so he doesn't have to walk around as much - it will wear ya out... trust me. Plus, better parking in the VIP area.
Good luck with it all.
And if you guys get into the pit/paddock area, I have something you need to get Rusty to sign for me.