pop festivals

Hi,  Not sure if there is an appropriate section to post this but here goes.  Our 14 year old son has just started to go to the odd gig & wants us to to take him and a friend to a festival this summer.  Can anyone recommend a resonable civilised pop festival that we could visit whilst staying at a nearby caravan club site? & if the site were near a decent theme park that would be even better.  I would love to here from any members who have done this sort of thing before because it is definitely out of my comfort zone. Thanks for any advice that you can give. Regards, kje.