Little petrol gopeds are well worth taking down with you. Last year we did miles and miles on them... 
To and from Arnage for food/beer, a few laps of the track, into town for the drivers parade on Friday (even joined in with the bikers at the end of the parade). Made it back okay too  

 If you get one though, buy a bottle to threadlock and lock all the things that can vibrate loose, otherwise they will fall off! I remember having to change (read bodge) the front wheel bearing on the grass verge at Indianapolis last year.
As for locking them up, we over looked that at the planning stage. When we took them down to the grandstand at the end of the race we left them outside cabletied to the railings, they were still their a few hours later.
This year we have a Merc Sprinter coming down full of them!
Simon