If you have a car, then take a driving tour of some of the high Alpine passes with him. There's some stunning geology to be seen from the road that I would think a Geographer would be interested in, and it's easy enough to find somewhere to park and go for a walk to see it up closer. It's a great time of year for hiking, just bring a fleece and a jacket when heading up high. A lot of the cable cars are still running, albeit on slightly reduced schedules - tourist offices can give you more info.