How long are you up for?
If you're heading to Islay, then you might want to consider Arran too? You could add it to your itinerary without too much hassle. I don't the island terribly well but it would certainly tick the box in terms of a country location. You could then get the ferry from Lochranze to Claonaig and from there it's a reasonably short drive to get the Islay ferry at Kennacraig.
Once you're back on the mainland you can head up to Oban or even push on to Fort William if you want to base yourself somewhere to get the Jacobite Steam train and explore the wider area. Glen Coe and Glen Nevis are close to hand and you there are plenty of easyish walks you can do with the kids.
If you're driving you could retrace the journey to Mallaig that you did on the train and get the ferry to Skye. Explore Skye (would need a whole other thread!) and if it was me and I had time I would get the Glenelg Ferry
. It's known to be a wildlife haven and you have the option of exploring the brochs at the other side. I think Glenelg Inn
has a pretty good reputation if you were needing another place to stay that was away from it all. From there it's a spectacular drive up over the Mam Ratagan pass and there's the option to detour back West if you want to see Eilean Donan Castle. Alternatively you can ignore the Glenelg ferry and go via the bridge and get to the castle that way.
From there head through Glen Shiel towards Invermoriston and Loch Ness. You could stay in Inverness if you fancy a bit more life but places like Fort Augustus and Drumnadrochit are picturesque in their own right and have a good selection of places to stay. The Loch Ness Inn
in Drum is owned by the same people who own the Applecross Inn and the food/accomodation is of a very high standard.
Route map: https://goo.gl/maps/ZbQe8JcvvSA2