Currently have a 2 month old baby, and we're hoping to get away in early-mid September for about a week (he'll be about 3 1/2 months)

Ideally we'll have a cottage or villa with a decent view, certainly not in cities. Will hire a car from the airport (Geneva/Basel/Zurich - somewhere where BA fly)

Is the weather ok in September? Any idea of a reliable site where I can book a villa?