In Kent good beaches are: Whitstable (shingle), Minnis Bay (huge & brilliant for sandcastles plus ample parking, loos and cafe), Viking Bay (middle of Broadstairs town centre), Botany Bay (v.limited parking, fluffy sand, no amenities), Joss Bay (huge, great for sandcastles, okay parking but v. steep slope to get down), Margate (donkey rides etc, parking but grotty). All above are reachable by train too.