In the keys it can be difficult, as finding an anchorage for dozens of boats
will be tough, but maybe not impossible. Marinas are expensive and as you
note, won't have enough trainsient space for a large club.

Several years ago I joined a friend's yacht club Maine cruise off and on
over a two week period. The organizer had set up moorings for all
participants in each harbor that they planned to spend the night in. The
cruise had about 25 boats. It was quite a challenge, but they pulled it off.
Even in Boothbay, Maine, they had enough moorings for all of the boats.

It was amusing when on one of the 15 or so nights they anchored instead of
moored at Wreck Island for a clambake. It was a hoot to watch all of these
sailors who had never anchored before. One brand new Sabre 402 tried for
about an hour to get his anchor to set with a 2:1 scope. I dinghied over and
offered to help, suggesting he let out all of his chain rode. The anchor
caught immediately.

So, it can be done, but it is a lot of work. I suspect most club cruises are
like the Maine one: most people want to stay on moorings and not on the
hook. But they don't want to stay at marinas either.

David