Hi -
Walk Highlands really will be your friend on this trip as far as hiking goes.
The ascent of Ben Nevis via the ‘Mountain Path’ (formerly the more innocuous ‘Tourist Path’ - I guess they changed the name to put off the casual walker in tennis shoes and shell suit with a Morrisons carrier bag with just a six pack in it, like the guy I once met on a descent!) is straightforward if strenuous, the only real potential danger being the proximity of gullies on the final approach to the summit. That said, a line of large cairns mark the bearing/direction to and off the summit (not the line of the path). The path, heavily scuffed by countless pairs of boots, is visible on the ground and obvious in clear weather - see photos on WH website route guide. You could always set off and see how far you got - no shame in turning back if it is too much or taking too long - you would not be the first and you certainly won’t be the last.
Other walks on the website are the Pap of Glencoe (fantastic views on a clear day) from Glencoe, Coire Garbhail from Glencoe (but there’s an unpleasant, if brief, boulder field to get in and out of the Valley), Stob Coire Nan Lochan from the roadside car park overlooked by the Three Sisters is another strenuous but largely straightforward walk except the final steep climb to the summit. I also like the ascent of Beinn Na Callich from Kinlochleven (it’s under the Mam Na Guillain Circuit) and easier than it looks from the track in - don’t do the full circuit, retrace your steps as the descent from Mam Na Guillain is rough, indistinct, tiring and with the potential to get wet crossing the river back onto the main track.
Hiking on Skye is exceedingly tough (but exciting!) and can be daunting for the inexperienced. However you can get a taste by following the track from Glen Brittle campsite up to the lochan in Coire Lagan where you’ll be surrounded by the Black Cuillin giants. Overwhelming! Retrace steps out. Obviously there’s the easy walks into the Quirang and up to the Old Man of Storr much discussed here and on You Tube!
I may be pitching stuff that is way too ambitious for you, but I suggest a thorough consultation with the routes on the WH website to give you an idea of what you might want to attempt - and what you might not. Most hiking in the Highlands has an element at least of very steep ascent, but you may want to plump for flatter, less strenuous walks - again the WH website will advise.
Hope you find something in each location to suit. Feel free to ask by PM if you need any help or advice - I’ll do my best to assist based on my own explorations!
Ian