Site within an hour(ish) of Dover

Essential

We will be travelling back from France to Dover on a Thursday evening and want to stay over somewhere for 3 nights before heading back up North on the Sunday when the traffic will be quieter.

 

Can anyone recommend a site that is about an hour (no more than an hour and a half) away from Dover to spend a couple of days with the kids.  I am thinking maybe seaside or resort town where there is a bit of something to do.  I have already had a look at
the Abbey Wood site in London but they want £95 for the 3 nights and it is just too much.  It doesn't have to be a CC site either.

 

Any suggestions please guys?