I'm on Windermere at present but intend to go back to the sea this season. There's a variety of "marinas" (at least, places with jetties) where you can berth your boat and enjoy 24 hour sailing because there's no tide. Depending on the size and draught of your boat, you may have problems on some of them. It's good sailing with young kids because its pretty safe and there's plenty of popular tourist places to stop at frequent intervals so they don't get bored. You can even anchor up and "cast them adrift" in the tender at lunchtime without worying about the tide. On the downside, however, its extremely crowded and lake access is restricted so if you want a mooring, you need to have it somewhere that allows you to park and launch a tender. Its also eye-wateringly expensive compared to marinas on the North West coast.
If its a swinging mooring you want, I happen to have one which I'll be looking to dispose of in March/April! Basically, you pay South Lakeland District Council an annual fee to have your mooring somewhere on the bed of the lake, then you buy the mooring itself and then you pay for someone to lay it for you. The latter needs to be done every few years for an inspection but isn't expensive. You also need to register anything with an engine but as long as its not a 500bhp ski boat, that's pretty cheap too!
Ullswater is much less crowded but they have a limit of 25 feet boat length. Ours is 27 so we never made it to Ullswater but I think they'd probably stretch a point if you asked nicely. I'm not sure if there are any public jetties and there's also less for a young family to do round the lake. On the other hand, its much cheaper than Windermere. You need to talk to a chap called Bryan McDonald at the Dalemain estate. They own the bed of the lake and issue mooring licences. Craneage might be a bit of a problem unless its small enough to launch on a trailer.
Finally, I have a colleague who ket a trailer sailer somewhere on Coniston for a year but have never kept a boat there myself.
Send me a private Message and I'll root out some contact numbers for you if you like and we can discuss other issues further.