I made sure to share the history of our team driving to their first games (poor kids): Devaney, Osborne, Berringer so when they see the statues it is more meaningful. I tell them about the traditions of the balloons, the tunnel walk and how Nebraska fans NEVER leave early regardless of the weather (this worked out really well because they are afraid to ask to leave).
Just like everyone mentioned - hit the north stadium area to see the trophies, weight room, waterfall. hit the east stadium entrance for more history. On the North side of the stadium is a track and next to it is a field that they allow kids to play in (I can't remember the name ) Usually there are games, balls to throw/kick and most important this is where you can pick up red balloons. Do this activity last so you don't have to carry the balloons for hours.
I found the easiest way to get into the tunnel area is to go down to the field level from your seat and walk alongside the fence to the northwest corner (by the tunnel door) and underneath the stadium and you will see the red carpet. Get there early as there will be a line!
Hopefully you'll see the players arriving at the north stadium doors and the band arriving about an hour before kickoff. No doubt they will have a blast. Enjoy and yes take lots of photos.