I'm not sure I can help much but I was in that area during the summer on a motorcycle tour. I stayed in Aix Les Bains for a couple of nights before moving on to Sisteron. We had a great ride around Annecy and on to Chamonix/Mont Blanc one day. Not sure if I'd like to pull my caravan around those roads though as they were very tight and very steep in places.
The route we took to get there was via the Portsmouth/Caen ferry, an overnight in Bourges then on to Aix Les Bains. It's about 550 miles to that area depending on route etc. You might do it it quicker by using the Peage, I tend to stay on the quieter roads when I'm on my bike.
The kids will love the countryside etc, but look out for sheep, goats, cows and whatever else walks in the road! You also drive up into the snow line a few times around there so be prepared for that.
Hope that helps a bit.
Mark