1) Don't get a Transit. I've had two; both died of rust (but I do live about 5 yards from the beach...)
2) Lightweight box trailer. We've been using one for two years; it's less than 2 metres long inside, but stows 24 sets waterproofs, 24 standard lifejackets, 4 infant lifejackets, 1 tender o/b, 2 paddles, various pumps and spares, publicity material and other bumph - and we can use it for advertising. It also cost less than £1500, doesn't use diesel and doesn't need road tax...
3) Don't get a Transit...