Some random notes:
Sewer tours are closed on Thursday and Friday IIRC.
We wanted to visit the Pompidou center area but ran out of time. This one stays open late on Thursday IIRC - I also wanted to take a photo of the Stravinsky fountain which is in the vicinity.
Versailles was the highlight of our two-day visit, though it took up until about 4 pm of one day. We obviously could have spent the rest of the day - and more - had we had the time (but we were prepared to leave the rest for the next time, based on time of day). Being from FL, we don't get to experience the fall that folks up north do. So, a walk in the gardens - though time-constrained - was a nice experience. One downside was that the big fountain behind the palace was undergoing renovations (as of within the last couple of weeks), so the gargoyles had been taken down (and with that went one of my photo ops). I doubt very much that they will be done by December end, but what would I know? Also, we encountered no - let me repeat - NO lines at Versailles (Friday morning), Louvre (Friday evening) or Orsay (Thursday evening). I was really amazed! That said, I don't know how crowds in late November compare to crowds in late December.
Since you also referred to arriving early (at Versailles), let me share our experience. My family was notoriously tough to get out of the bed. So, the first day I left by myself to check out the underground. Went from Michel Bizot to Chatalet and back by 9 am just in time to catch the rest of the family just about getting ready. What was ironic is that though both my weather channels had indicated a 10% chance of rain, it was raining in the Chatalet area when I walked out to the ile de cite (sp?). The second day, though I had told the kids that they need to be up and ready errrrrly, they repeated their performance. We were able to leave only around 9 am or so (maybe 9:20 - I need to check the photos to figure out the correct time). We got into Versailles - the Chantiers station not Rive Gauche - and (literally) walked into the palace after a 10-15 minute walk.
Of course, check the weather leading up to your trip and be prepared to go with plan B if weather is a factor. We lucked out and did not have it rain (or snow) on our parade. That said, looking at the last two weeks' weather, it appears that ours was pretty much close to the worst in that time frame - and we still enjoyed out visit. We followed both weather.com and weatherbase.com for two opinions :-)
Douglas: I didn't realize that the gargoyles were fake. I am assuming that, by fake, you mean they were added on to the structure in modern times. Well, that at least helps my sour grapes moment because both days we were there, we were unable to make it on time to Notre Dame as the access to the Tower apparently closes at 4 pm (or so).
I haven't gone back to the map to see what it was, but the museum/building immediately to the west of Orsay looked promising the day we visited Orsay. We were obviously there after closing time so we could not get in - but whatever we saw appeared war-related stuff. Is this the Napolean museum you were referring to?
Norma/Janet: I had the science/air museums (there are two or three of these) in my long list (short list I posted in one of my threads) but I knew there was no way we would've made it to any of them. My idea was to see the unique ones first then go for those that could be seen in the USA itself (at least similar to those).
Hope this helps.
Porcupyn