Head ache of the young

We live in South Devon and have a fibe year old that loves going away in our caravan, all our other children are a lot older and very rearly go away with us any more, he has been begging us for the last 18 months to take him to legoland in Windsor but it is such a long drive for a day trip and the new hotel on site is so expensive. Can anyone recomend a site, full or CL, near to legoland that is reasonable in price for a couple of nite stay please