I've never been to Mont Blanc but after doing a little web-searching, and thinking about my own outdoor trips, I think most of the pics he'll value will end up being people - he and his fellow climbers - and many will be taken at short range with dimmer lighting - the overnight hut, early morning and late evening, maybe bad weather days - or shadows - squinting faces under full daylight. So the sweeping Alpine vistas in brilliant mountain sun, that I initially envisioned, will be only a minority of his pics.

Given that, I think there's a lot to be said for a quality point & shoot. Minimal bulk and weight, indeed he could even carry a spare. Fits in a pocket where it can stay warm/dry. Can operate with a single gloved hand. Likely to get at least passable pics - in focus, exposed more or less right. Flash for pics of the overnight camp, and also fill flash for daytime. Decent zoom range. Slow lenses probably okay, given flash and/or outdoor lighting.

If he's more inclined to manual photography, I'd think a compact rangefinder would share a lot of the above virtues.

So personally my investigation would start with:
- Olympus Stylus 100 Wide: 28-100mm, flash with fill mode, claimed weatherproof, metering modes claimed to include spot. I've never used one, I just looked up the specs since I liked my older Styli, but on paper it seems to fit the bill.
- Olympus XA w/ A11 flash: the manualist's choice. Will be great for the daytime shots (set on f8 and infinity) but less so for the overnight. Very nice lens, but no zoom.
- Rollei 35 w/ flash: the traditionalist's choice. Probably too fiddly for someone who isn't already familiar with the camera to take up Mont Blanc. But if he gets an old one with a corner dent, well, it may well have preceded him up Mont Blanc!

I'd also consider taking a tiny table-top tripod.

Finally, you should advise him as to the type of film, too. I'd want at least one roll of something with saturated colors for overcast days.