There is a small caravan site on a farm called Gillside in Glenridding Ullswater, there is only about 20 vans on it. It is not a commercial site though and is absolutely beautiful. It's a great place to stay with a stream running next to it. There are 3 great pubs within walking distance of the farm, you can also start Helvellyn from the farm if you're feeling fit. This is a lovely part of the Lakes and not as touristy as some of the other places there.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.