Fingers crossed - France in December

Hopefully the Christmas Markets will be in full swing. Strasbourg is absolutely stunning at this time of year. I took a day trip to Colmar - 5 smaller markets. The villages will go all out for Christmas too. I’ve been to Annecy several times but not in winter - it’s a beautiful place. Doubtful the tour boats will be running but after a year of lost revenue, you never know. If my geography serves me correctly you will get a better French alps experience in Chamonix.
I’m hoping Germany opens up as well as I very much like some the Christmas market in Rudesheim.
Have a fun time!

There's a decent Christmas market in Montreux, an easy train ride from Geneva. My understanding (and it could be a flawed understanding) is that it's one of the larger ones in Switzerland. Not as big as Strasbourg, of course, but still pretty good.

If you're going to be in Geneva at that time, I also would consider a short hop to Lyon via train to catch the Fête des Lumières. It's a blast. And Lyon has some decent restaurants to boot. The 2021 Fête des Lumières is scheduled for December 8 - 11. Search on Youtube or other video platforms for videos to get a sense of what it's like.

Edited

Here's a video from the 2019 Fête. That's the last year I went (probably the last one they had pre-Covid). I especially liked the giant illuminated puppets. It's amazing how natural their movements are -- the folks controlling them really have it figured out. And it's not just lights -- it's music as well. Worth a visit.

I'd give some of that extra time to Paris. You've been there before, but you know there's much more to see and do than 2-3 full days (3-4 nights). And it should be great whatever the weather is, and it will save you time moving around.

Reims has a beautiful (mostly restored) cathedral, a good Roman gate, an important WWII historic site (I think the 1945 surrender), and all the Champagne you care to learn about and/or consume. Easy by rail from Paris, but I'd think a couple of nights and partial days would be enough.

I didn't find Reims a particularly attractive place by French standards (which are quite high, in my experience). The highlights have already been mentioned. The Porte de Mars was swathed in something opaque and trussed up like a shipping carton at the time of my 2017 visit; whatever they were doing to it may have been finished up long ago.

There's a lot to do in Lyon; 3 or 4 nights there wouldn't be too long. It's not far from Annecy. I recommend it highly.

Thanks for all the great input thus far. I had the same thought on Reims but my husband threw it out as an idea so I figured I'd ask. ;)
We did go to Lyon (briefly) on a prior trip and I had considered adding it. The light festival is a fun idea, too - we saw one when we were in Jerusalem in 2018.
I am weighing Annecy vs Chamonix. I really enjoyed our brief time in Annecy but am afraid it will lose some of its appeal in December.

Gonna add a night in Paris. :D

Celeste, We will be in Paris, Colmar and Annecy at the same time you will be (hopefully!) and we're thrilled! We've been to Strasbourg, Colmar and Annecy at that of the year before and the Christmas markets were incredible. Annecy had a few markets as well, and although it was cold and a little rainy, we loved our time there. When we were chilly we popped in a delicious restaurant for crepes!
A couple of notes: We've also been to Montreux's markets and they were slightly different and rows and rows of chalets! (More commercial than Annecy, Colmar and Strasbourg.) The lake is beautiful, and we saw Chateau Chillon while in town. However, I'm nervous about adding Switzerland...do you think they will be open as well? Switzerland seems more cautious than France, but maybe I'm wrong. Also, will Chamonix be too snowy at that time of year? I don't know, just wondering! If so boots and warmer jackets may be hard to carry. Maybe someone can speak to that?
Good luck on your planning, I'll be listening for the good advice you get for the trip!

While Chamonix itself is unlikely to be very snowy in the 1st half of December (might still happen, though), the various surrounding viewpoints and mountain excursions will probably be cold and snowy and you would need to pack accordingly!

I still think that Chamonix is a stronger choice than Annecy for any "outdoor guy" who wants to see the French Alps: in Annecy you have mountain views, in Chamonix you are IN the mountains. Hiking expectations need to be managed, however: short days, wet and slippery ground... really not the best time at all, and too early for snowshoeing or proper winter hiking.

Amanda - We are not going to risk visiting two countries this year. Tracking one is enough stress.

I decided to home base in Colmar and train up to Strasbourg to cut down on the moving around. We'll take the train from Paris to Colmar, rent a car in Colmar for seeing that area and driving down to Lyon and maybe keep it all the way back to Geneva.

As of now the plan is Paris 4 nights, Colmar 4, Lyon 2, Chamonix 3.

SIL is most excited about Chamonix. He is an experienced hiker (he works in the Smoky Mtn National Park) so I'll let him figure out that part while I drink hot cocoa by a fire.
Accommodations in Lyon are very expensive for the days we are there (I guess because of the light festival?) so right now I'm only planning 2 nights. Found an apartment on booking.com in a good location that was reasonable so went ahead and booked it (refundable). I searched for it to book direct but it wasn't refundable which is a bummer.

Oh that's why Lyon is booked up! I noticed that as well early in our planning. I think you have a great plan and it all sounds amazing!