Hi again, JW65,
The boat trip from Elgol to Loch Coruisk, if that's the one that you plan to take, is actually on a sea loch (Loch Scavaig), not out on the open sea. So it's normally a calm voyage. Having said that, we were in Elgol last July after a long hike, and we saw the Bella Jane coming in to Elgol in a squall. She was bouncing from side to side (port to starboard?), and the passengers looked very happy to reach the jetty.
If there has been heavy rain the day before your hike, you may wish to reconsider, as the hike involves a crossing of the River Scavaig on stepping stones. On a dry day, this is no problem, but if the river is in spate, then best not to attempt. The hike is about eight miles. It's well marked, especially after you reach the top of Druim Hain. Once you get down in to Glen Sligachan, it's fairly level. Believe it or not, the hike is not on the WalkHighlands website. It is on the AllTrails website, although the route provided includes a circuit of Loch Coruisk, which isn't necessary if you are heading on to the Sligachan Hotel.
You could still take the Bella Jane out to Loch Coruisk, and stay near the south end of the loch until the boat returns. It's about 90 minutes between landings. Loch Coruisk was a favourite travel location for the Victorians, as authors and painters had created what we would call today an urban legend about its inaccessibility and austere beauty. It's still impressive today, moreso if you hike a bit up the western side (very boggy) to see the top end. It's surrounded on both sides by the Cuillins, and is very atmospheric on an overcast day.
The Bella Jane does make other trips, under their AquaXplore branch, but most of them are in an RIB, which I'm sure that your husband would not enjoy! If you're interested in visiting some of the Small Isles, CalMac has ferries leaving Mallaig which allow you a few hours on either Eigg or Rum. The schedules are a bit convoluted, but once you figure them out, they make sense.
Best wishes once again!
Mike (Auchterless)
p.s.: There are some nice hikes on Raasay as well. Raasay is a lot less busy than its larger neighbour.