In reply to Orgsm:
Depends a bit on how fit your Dad is (and how rich). Swiss huts (like everything else in Switzerland now) are very expensive. Tour de Mont Blanc has fantastic high mountain scenery, but has some big up-and-down grunts and can get busy in July/August. I'd endorse Orgsm's suggestion of the Vanoise - beautiful country, fantastic flowers & wildlife, excellent friendly huts, bags of scope for permutation and variation of circuits and loops for up to two weeks, various easy non-technical 3000+m peaks you can do along the way. You can always cross into the Gran Paradiso National Park in Italy for a bit of variety. It's all in euros so good value at the moment. You can start from Pralognan (my favourite) or from Modane as well as from Val d'Isere. And if you enjoy that, then you could graduate to the Tour de Mont Blanc in 2017.