I did it when I was 16, my dad went down with me and did PDC on his 06 M5. It was an awesome experience.
I learned so much about defensive driving and experiencing high speed lane changes and abs braking. In my honest opinion that is what every teen should go through before they get their license.
I know that my dad hung around the PDC while I drove (I'm pretty sure it was only a day long) and my little sister just went a few weeks ago.
Can't really comment on what there is to do, you might be able to see some of the driving from the building but I don't believe you are allowed to spectate necessarily. I just thought it was a fantastic experience for myself as your other kids I'm sure have said.
Enjoy the trip