dolphinne,
KGC's comments about Normandy in the winter are spot on. For your son, WWII happened all over Europe. The DDay invasion at the Normandy beaches are just one part of that years-long war. I would check out the many, many sights in France that honor and remember WWII. There are even Paris museums. The Invalides (army museum) in Paris is huge and covers centuries of French military history that could pique his interest as well (I love the suits of armor). Plus Napoleon's tomb is there. The area around Lyon was central to much of the French underground movement during the war, so you may find some museums/memorials in that location. There is no need to limit yourselves to the DDay beaches area.
The weather in the Alps in December could be iffy. What exactly are your aspirations for a visit there? Maybe use the search bar above for specific comments on Chamonix and Annecy in December. With your limited time, I would save that area for another trip.
I do suggest you make your plans by counting nights, not days, and making sure that you are accounting for real travel time between places. Do you arrive on 12-1 and depart 12-15? If so, 12-1 will be kind of a "not doing much" day as you get through immigration, travel to first night's hotel, and recover from jet lag. 12-15 will be all about departure. That leaves you 13 full days to enjoy France. Take away at least half of a day for changing locations (and maybe a whole day depending on your route and destination) and you lose maybe 3-4 days (dropping Chamonix). You now have 9 or 10 days, with maybe a half-day once or twice if you get to your new location by early afternoon. And there would be no time for the south of France this trip.
Re ChatGPT...Someone on the forum posted an AI recommended trip for their time in Europe, and it made no allowances at all for travel between places. The only way it would have worked was with a teleportation device. And it only allowed for about 1 day in each place. Perhaps you could just take a look at a map of France to see where all the places are in relation to one another, then check travel time between them, either by car or train or both. Add in time for checking out of lodgings, getting to station (if applicable), getting to new lodgings and checking in. If driving, add in time for gas/food/comfort stops to drive time. (viamichelin.com is a good source for driving routes and times). Also, allow time to find your way around in each new place and where to park the car. You may find that you want to drop another location.
If you kept all but Chamonix, and use a car after leaving Paris, I would make a counterclockwise loop: Paris to Normandy to Loire Valley to Lyon to Alsace (Strasbourg/Colmar) to Paris. Save Paris sights for the end. 12-1 sleep in Paris; 12-2 train to Caen, get rental car, drive to Bayeux, see what you can in the afternoon, sleep Bayeux; 12-3 See what is open in Bayeux in the morning. and in the afternoon, drive (about 3-4 hours) to Amboise in the Loire valley, sleep Amboise; 12-4 visit chateaux (2, maybe 3 if you rush), sleep Amboise; 12-5 drive to Lyon 5-6 hours, sleep Lyon; 12-6 and 12-7 visit Lyon and nearby sights, sleep Lyon; 12-8 drive to Alsace (Colmar) about 5 hours, sleep Colmar; 12-9 visit Colmar and maybe a nearby village or two, sleep Colmar, drop off car; 12-10 train to Paris, spend rest of nights in Paris (12-10 through 12-14. That gives you 4 full days there.
It is all doable, but please factor in travel time, whether train or car. As far as trains go, note that many trains from place to place go through Paris, with a change there. Think of a wheel with spokes. Also, you will want some do-nothing down time. I have traveled with our kids at different ages, and when they were your kids' ages as well. Try not to fit in too much stuff. Give them time to absorb what they see.
