Failing that I might have to throw myself on the mercy of the UK weather and take him sea-cliff tradding at the likes of Pembroke/Bosigran although the tides look pretty rubbish.
The problem I've now got is that I'm struggling to think of Euro-venues that offer big, easy climbing away from the alpine setting and weather risk that goes hand-in-hand (given the proposed time of year).
They'll have to be really rubbish to rule Bosigran out.
Some easy 5+/6a routes in Riglos that get you to a summit
I did think about Mosquitoes but then what? I've had Nat struggle on a few stiff 6's at Riglos which worries me with Dad. It'd certainly be a good objective to add as a part of a wider trip.
How adventurous do you want to be?
Tafraout? I've not been but a friend has done Labyrinth Ridge on Aylim, an 800m VS, and enjoyed the whole experience. Wadi Rum has lots of this kind of thing, again go for the experience as much as the climbing.
I was going to suggest the VS on the backside of the Naranjo de Bulnes until I noticed the time of year you're going. I think October would probably be too late in the season.
I watched the Petzl Rock Trip Meteora video and thought it looks awesome (and surely there's plenty of easy stuff):
Jacob Cook makes it sounds as though the easy stuff at Meteora is quite exciting... http://jacobclimbsthings.blogspot.co.uk/2014/02/meteora.html