Until your in there you will never "get" just how big the site is (trust me, was blown away 1st time)
and the distance you will walk with all your stuff will depend on which carpark you come in?
Cockmill meadow's great for younger kids,my sons 10 and just gets up and goes but my 15 yr wants us to camp elsewhere (not happening)
Best advice i could give ya is.....Ask the stewards on the carpark gates to radio through and see which family camps are full, then head to the carpark closest to where your camping
in answer to your question, would you have to walk.......Hell yeh! 1st time i walked the whole way across site with all my stuff ,
so asking 1st is the key

(wish somebody had told me hahaha)
Good Luck