UPDATE on the Garberville alternate for people who I haven't contacted by private message:
I've contacted several of the shuttle firms that normally transport hikers or do area tours, and the following two have indicated they can be available to anyone needing transport between Garberville airport and Shelter Cove in case the latter stays fogged in on arrival days from Thursday to Saturday (with a Sunday departure):
Roxanne of Lost Coast Trail Transport Service responded to my email with an email that said that she has done this sort of transport before; understands about the fog, and would know to expect calls if Shelter Cove stays fogged in. She could be called on her land-line (707-986-9909) or cell (707-273-7414) for a fog report. She can carry up to 3 people on a trip and the rate is $120. No deposit is needed; we'd call if/when we needed her service.
Blu Graham at Lost Coast Adventures responded to my email by suggesting we talk on the phone. For a single trip the price would be between $80 to $100. If the pilots are packing light, it sounds like he could carry 4 or 5 people in one trip, lowering the per person cost. So if we can manage any sort of scheduling coordination on landing in Garberville that may help. Otherwise there would be a 1.5 to 2 hour wait between shuttles, since that is how long it would take to go from Garberville airport to Shelter Cove and back again. (This of course would be the case with either firm.) He also said that if he had to do a lot of shuttling his cost would be at his hourly rate of between $40 and $50/hour.
No deposit is needed for him either, and he has already penciled us in for Friday, Saturday, and Sunday. He would schedule in hiking groups on those days anyway, but presumably keep some flexibility in his schedule in case we needed his services. He asked that I contact him 7 to 4 days before any of us arrive to let him know if other weather precludes us from even getting in. (He says he has a friend who is a local pilot and was willing to provide that pilot's contact information if we wanted a local source of weather. I said we already had a hotel innkeeper who could provide that info.)
The price range given by Graham is due no doubt to this being the first time he has considered offering this service. The above all comes from notes I took during our phone conversation, hence some ambiguities.
I have not settled on one firm, but I think I probably should. Should I simply go with the cheapest, or the more experienced?