I went to the 2 Champ Car races at the Speedway. They ran the event with the NASCAR trucks, which were on first. For NASCAR, you're probably going to have a sell-out crowd or close to it. Just count on extreme traffic delays getting in and out, since there are only 2 exits from the Speedway (to the 15 freeway and to Las Vegas Blvd). Give yourselves plenty of time to get in and plan to relax in the parking lot for a very long while before attempting to leave. As I recall, the facilities were good at the Speedway. Good views from all the seats. There was a variety of food and drink available.
I'm more accustomed to being at the road course, just outside the Speedway oval, for vintage events. But, those 2 Champ Car races on the oval were fun (except for the fact that oval races with open wheel cars always made me worry about driver safety).
As long as you give yourselves plenty of time, I think you'll enjoy the Speedway. Just note that it is a decent distance from the strip. Plus, it can get quite cold and windy in that area. If you come in on surface streets (LV Blvd takes forever! You can also do 15 fwy to Craig Rd to LV Blvd), the surrounding area is pretty sketchy. If you don't want to eat at the track, there are some good restaurants along LV Blvd before you hit Craig Rd (coming from the strip) and on Craig Rd on the other side of the 15 fwy around the Cannery Hotel and a couple miles past it.
If the race is during the day, be ready for some possible fighter jet noise from Nellis Airforce Base next door. They fly over all the time when we're there for vintage events and those suckers are loud!! Chances are, the Thunderbirds will do the fly-over before the start of the NASCAR race.