Hi, ephemeral,
In mid October, you'd have about 10 hours of useful daylight. If you're planning to visit Loch Coruisk, there are two ways to do so: You can take the Bella Jane from Elgol to the Loch Coruisk jetty. They give you approximately 90 minutes to six hours to explore the loch. A lot may depend on the daylight hours. However, they don't combine the Loch Coruisk trip with the Small Isles trip, so given your time on Skye, you'd have to choose one. The second way to visit Loch Coruisk is to hike in from the Sligachan Hotel (The "Slig"). However, this is an eight mile hike, and unless you've made arrangements to be met at the Loch Coruisk jetty, it's eight miles back. (See below)
Unless you see the loch from a high vantage point, it's not that impressive. You can hike around the shore (it's extremely boggy after a rainfall), but if you only stay near the jetty, you can't see all the way to the north end.
If you're coming over on the ferry from Mallaig, I'd recommend spending a day there and taking the MV Loch Nevis to either Eigg or Rum. It's possible, depending on the day of the week, to land on either of those two islands (but not both!), and spend a few hours. That would give you your visit to one of the Small Isles, and give you a full day for the Bella Jane trip to Loch Coruisk. If you choose, you can stay on the Loch Nevis and pay non-landing visits to three of the Small Isles. You also have the opportunity to see marine life from the ferry. It's possible (but not practical) to visit the Small Isles then take the last ferry from Mallaig to Armadale. I would not recommend it.
One caveat here: The Small Isles service cuts back considerably after October 17th, and the ferries are notorious this year for breaking down. That's actually two caveats!
It's a long drive from Portree to Elgol, so if you're taking early passage on the Bella Jane, you'd be better served spending the previous night in Broadford. I'd recommend taking the Bella Jane on your first day, then using Portree as your base for the Trotternish, Waternish, and Duirinish Peninsulas.
Some smaller restaurants may be closed by mid-October, but most of the hotels will still be serving non-residents, and the "Slig" is good for meals year-round. You can also get pub meals, and the "chippies" in Portree and Broadford should still be open. The Cafe Sia in Broadford should be still open, as a lot of the hostellers from the village eat there. If it's still on the menu, try the Highland Melt.
Speaking of the "Slig," a few years ago my wife and I took the Bella Jane from Elgol to Loch Coruisk, and hiked over the Druim Hain down in to Glen Sligachan. What I thought would be a four hour hike turned in to an eight hour hike, and we were mercilessly attacked by clegs as we hiked along the glen. It took so long to reach the "Slig" that we missed the last bus back to Broadford, and had to take a taxi all the way back to Elgol. My wife was not pleased! Happy to say that we are still married!
I'm sure that Jacqui will be able to provide you with more local information. Skye is quite spectacular year round, although most of Western Scotland is as well.
Wishing you happy travels! Is there room for me in your suitcase?
Mike (Auchterless)