In reply to Owen W-G:
Depends on your budget really. Towing a fairly big family to Lakes for many years we went to Greenhowe Holiday Park in Langdale. Mainly static caravans but some very nice lodges too. If money no object there are loads of other options around Ambleside and also Coniston which are never too far from some sort of entertainment/civilisation!
We found that overall for a family break the SW Lakes had more to offer than the North (that's not to say that Borrowdale, Keswick aren't good, they are lovely!). The other place we stayed, but many many years ago was Limefitt Park Troutbeck which is very handy for Windermere, but I think has gone a bit up market since we went there!