You certainly have a dynamic
learning experience ahead of you! Some people have gotten away with SneakaBoarding but it can end up with a nasty experience if you are caught and they evict you in the middle of the winter and forbid you to stay onboard as of right now. The whole issue of liveaboards is in major flux but, as always,
marinas and marina managers have different ways of enforcing the rules.
Not every marina has good protection from winter winds. Some people will tolerate high winds and poor protection in exchange for low rates. You'll just have to ask the locals how it is. The worst winds, in the
San Juan area, are from the north and from the southeast, with the longest and fiercest mostly from the SE. But the islands have squirrely
wind patterns with different winds on varying spots even on one island.
I would not recommend living on a
mooring at all in the winter unless you are OK staying on for days at a time, on an unplanned basis, and wet if not too exciting
dinghy rides to and fro. You might even get stuck on shore with the dink when a storm comes in and makes it life threatening to go out.
Sounds romantic and
cheap, but I think I am pretty safe in saying that once you try it you will never do it again. But, hey, some people like that kind of adventure. The fact of the matter is that it is challenging just living on a
boat in a marina in the winters here. Many do it but it is a radical change in lifestyle what with long cold/rainy walks to the heads/showers/parking lot/etc. But since you are already doing it now it may not be so hard to adapt. Having done it both in the winter and in the summer, I can say it is exponentially different in the winter with not only stormy/wet times but also the short days, low sun on the horizon, long nights, and heavy clouds. But, this coming winter may be much drier and sunnier. It is going that way.
The other issue is being close to necessities such as groceries and place to go to get some relief from the monotony of a small cramped space for a
family of five. Kudos to you that you can handle five on a 41' boat for extended periods already.
Deer Harbor would not be on the top of my list unless you want a dreary isolated experience. Very pretty and I have heard that the marina people there, and the island people, are very nice.
Lopez is a cool place. Not much in the way of amenities. Very small grocery store and a few other things (good ice cream!) and a very laid back island style. The harbor is somewhat protected, especially from swell and
ferry wakes.
Friday Harbor would be at the top of my list for amenities and is fairly well protected. I don't know about the marina mentioned above that is there. Friday Harbor is the closest to a real town/village in the islands with much more to do and places to buy the necessities without a
ferry ride all the time. The ferry wakes can be a PIA but that would depend on where you are docked. Roche Harbor is much more deluxe but is probably the most expensive.
Blaine is an option but not in the islands, at all! It is very exposed and is a downright cold place in the winter at the end of the
wind funnel called the Fraiser River valley. Perhaps I am overstating it but don't think so. Others can set me right I guess. The marinas have been upgraded I think. If you want something more exotic you could look in to Point Roberts where you have to cross the US-Canada border twice to get to it and back to the rest of the US. No idea about liveaboards there. You are very close to
Vancouver and surrounds which is pretty cool, but so is Blaine.
Anacortes is a possibility too as it is close to the San Juans and is an island itself (sorta kinda). Nice little town. It can be hard to get
liveaboard status and is not
cheap. It is easier to get slips in the winter as many people haul their
boats and put them
on the hard then. Some marinas require annual leases or no go though. But that just depends. Anacortes Marina is a condo marina and the owners who have
boats they use in the summer may be willing to do a short term
lease if the manager will let you. Not cheap though as noted.
People do it. I have several friends around my slip that liveaboard full time. But no big families. Actually no families at all. It takes a special
family to do that. Sounds like you must have one of those.
Good luck!