Aberdeen to Cornwall half way stop

KD2012

Hi.

We are travelling from Aberdeen to north Cornwall and want (hoping) to only have one overnight stop. Can anyone recommended a site close to M6 which is roughly half way  ( or even 1/3 as the Scotland leg will be the slowest) down? I know it will only
be for one night but clean loos and some sort of play area is very much preferred. no animals travelling unless you count the kids. many thanks in advance x