Chamonix in August

I have not visited Chamonix in the summer, but in general, Alpine resort areas never feel "crowded" like some popular museums, beaches or amusement parks may seem. The tourist infrastructure is usually built to accomodate thousands of skiers in the winter. The number of hikers that these same resorts host in the summer is generally a fraction of that number. The closest I've ever seen to a "crowded" Alpine location in the summer would be Zermatt, but even here, it was far from a horde of wall-to-wall tourists, and I only encountered a handful of people on a 5 hour mountain hike. I have never seen gondolas that you can pre-book. And it isn't be necessary anyway.

Some areas of the Alps do get a bit crowded in August. But not terribly crowded, and I don't think it would be a problem. One other area I would recommend looking into is the area called Portes du Soleil. It's a combination of many different resort/villages not far from Mont Blanc. A little more off-the-beaten-path than Chamonix. Good hiking and biking. Avoriaz is a great place, but more family-oriented as they have an indoor water park. But - they offer a "MultiPass Premium" for 2€/person/day that includes use of the sauna/hamman/jacuzzi as well as unlimited ski lift riding, mini golf, indoor water park admission and more. It's about 20€ more per day to get the pass that lets you take your mountain bike on all the ski lifts. No pre-booking gondolas needed. Getting up early is optional, but since some of the ski lifts close early, full day hikes do require getting up early.

We were in Chamonix in July and it was delightful, not crowded. It's a charming town and the hiking is absolutely wonderful! You can make a reservation for the gondola up to the Aiguille du Midi (12,605 ft) with a panoramic view of all the mountains, and then take another across the clouds to Heilbronner in Italy. You're up with the angels! Good food in Chamonix too. Bon vacances!

We were there a bit later in Sept last year. Not crowded at all. We stayed at L'Ostralet which is 2 blocks from the main gondola lift. We bought our tickets a day early and went up on the first runs along with the paragliders to Aiguille du Midi at 12,605'. No clouds so it was one of the best views on the planet. We could even see the Matterhorn in the far distance. Didn't need a jacket up there (but you might). In August, you do have the opportunity to take the second gondola from Aiguille du Midi to Helbronner in Italy. This second run was shut down for the season just before we arrived. Tons of really nice shops and lots of places to eat. We enjoyed La Caleche for it's good traditional food and a bit of nice rowdiness. We were close enough to Switzerland to have fondue. The next night we went to Atmoshpere for some fine dining. Both were great. One last hint. You mentioned Geneva. There is a minibus run from the Geneva airport to Chamonix. This bus departs every 45 minutes and goes directly to Chamonix. Fare is 29Euro. This is much better than the train which will take about 4 hrs and will require 3-4 changes. Here's a link. http://www.chamexpress.com/?gclid=CNiC1-rTxLECFWIGRQodNBgA7w