If you like wildlife, a big day out from Fort William would be to head to the Ardnamurchan lighthouse (dolphin / whale spotting) via the Garbh Eilean wildlife hide, Sanna Bay if you have time and then pop by Castle Tioran for the photo opp on the way back.
Mallaig and ferry to Knoydart for a few hours and Arisaig / Morar beaches.
A short wander up Neptune’s Staircase and wander along the canal, note the Lochy pub will reopen middle next week (covid positive case).
Gondola is good call. There are several shorter walks to waterfalls or to views around Glencoe / Ft William, see walkhighlands.
On Skye the Elgol boat trips are well regarded but you need to phone to book and be flexible.