Ullapool to Oban is one of my regular trips – lots of folk park at Oban and then need a lift back with their bikes.
I took a family of 4 from Ullapool to Edinburgh a few weeks ago. The youngest was about 10 though. They’d cycled through from Barra to the Butt and back to Stornoway over 9 days.
If you want to limit your cycling, I’d recommend the Uists. You could do a circular trip using the ferry from Mallaig to Lochboisdale, fit in a trip to Barra and then go north, returning via Lochmaddy. That would leave you a (hilly) trip through Skye to get back to Mallaig though.
There’s a great site at Balranald on North Uist with a beach beside it and it’s in the middle of a RSPB reserve. Anne does great cakes/scones/soup but the nearest shop is about 6 miles away so stock up en route. (I’m away up there on Sunday for a week 🙂 )
The Harris-Lewis trip can be really nice. Great views into Pairc and South Lochs, then over to the west side to see Callanish, Dun Carloway, Garenin etc. Return to Stornoway via the Pentland Road if you’re not going all the way to Ness.
Oh and book a meal at the Decca in Ness. Trust me. You’ll thank me later.