Greece Trip: Santorini overThanksgiving? Nafpoli, Delphi or Thessaloniki (or somewhere else)?

How many days/nights is your trip?

Cannot imagine that going to Santorini for one night would really be worth the bother/expense.

I wouldn’t go all that way for one night. The weather at that time of year could be awful.

The entire family is staying for 6.5 days/7 nights and 2 will be there for 12 days/13 nights. It would be an expense so was thinking it would not be worth it. Thanks!!

Flying will be expensive but more importantly it will take up at least a half day from your vacation. For the group with the small number of days that's a significant proportion of their precious time on a side trip with a high risk of non optimal weather. Santorini will be pretty much shut down but that doesn't mean the views have gone away so you could get lucky and get a nice day.
As I see it you might want to split up. If one daughter is adamant that she wants to do Santorini then let her go and see if there is a volunteer preferably one of the people with the 12 or so days available.

If you want to have the whole group stay together then a much better option would be to go to Nafplio for an overnight. Its a weekend get away for Athenian all year long. Its easy to get to with interesting stops at Corinth to see the canal and Ancient Corinth along the way. I read last year that Ancient Nemia closes for the off season so it may not be open in November. This way you will be able to experience ancient sites plus the Nemian wine country as well as one of the prettiest sea side towns in Greece.
Here is what you can expect.
Nafplio and Peloponnese http://www.flickr.com/photos/stanbr54/sets/72157632094108982/

I'll bet that the one daughter with her "heart set" is the younger of the 2 and doesn't want to listen to older sister w. more knowldge. I will further wager that the younger one has her image based on the movie "sisterhood of the traveling pants" which is lovely fable with no connection to reality. You might tell her she's darn lucky to be going to Europe as a young teen, and she'll have plenty of time to follow her trip fantasies when she's grown & on her own. Sigh. Sometimes I I get tired of reading about anxious parents trying to twist their trip into a pretzel to indulge the wishes of an uninformed offspring. PLEASE remember you guys are the bosses.

Actually it's the older one that wants to go. And she's out of college. I don't think they've even read that book or seen the movie. She wants to go for the architecture and hike the volcano. She's more into the beauty of the island rather than the "party" atmosphere. We do know we are in charge but have told them that if they plan something and really want to do it the important thing is that we are together as a family. It's all about the experiences!

We went to Greece for 2 weeks with our adult aged children and my daughter's husband (21-31) last May. I planned the trip for the most part, taking into account people's varied interests and tolerances. But my older son really wanted to go to Meteora because he is really into photography. So he skipped out of part of the time we had in Athens, rented a car and drove by himself there. He spent the night and drove back, joining us for the last night in Athens (but half of our party had to leave early for work so he missed our official last dinner together).

We, of course, had two weeks not one but think about how to manage a trip with adult children. We also did not mandate that we all do everything together (there were seven of including my husband's brother) but except for my sons going off for a day and a half by themselves in Naxos (where they rented an ATV together), we stayed together. But it was entirely by choice. (BTW, we paid for the things we did together but anything they did separately was on their nickel, which I am sure encouraged family togetherness.) I did consider suggestions when we were planning--my older son really wanted to rent a car on Santorini and after some discussion with my husband, we decided it was better than taking the bus (and it was the best choice since we were in Oia which is not where the buses are headquartered). But this same son was also the one who really wanted us to go to Meteora and I said no--it is another trip, we are going to see Athens this trip. And I told him he could do it on his own if he preferred. And that is what he ended up doing.

We had a wonderful trip and I am sure you will too.

Beth