Steve - in terms of mileage, this is possible in a day. It is a bit over 450 miles from Le Havre to Annecy. Providing that you have had a good night's sleep (in a cabin, not a chair!), it will take perhaps 9 or 10 hours allowing for reasonable breaks. My personal preference is always to make the journey part of the holiday and break it up into smaller chunks. Some of our most interesting stops have actually been at places we have just happened to discover en route to somewhere else. But, if it is important to you to get there as quickly as possible, it should be possible. If unforeseen circumstances intervene - very bad traffic etc, you can always make a last minute decision to stay over somewhere and arrive a day later than planned.
Enjoy your holiday!