Thanks for the additional detail. Sounds perfect for us as well. Adding to the list!

We absolutley LOVED Santorini. We were there 5 nights, and wished it was longer. I recommend you go there, and stay there!

We were in Athens for one full day, which was plenty for us.

Hello everyone, thank you again for all your suggestions and assistance. We had an amazing time! A quick summary for those who assisted and if anyone else like me finds this in the future:
- Athens: We had 2 days and touristed long hours. Could have used one more day; I have a list of what to see when we return. The city is safe, clean, wonderful. We had an airbnb under 150m from the Acropolis metro station and the location was perfect. Recommend God's restaurant.
- Naxos: So pretty, so nice, so calm. Rented a car for a day and saw many parts of the island. Loved it here. Everything is close and people wonderful there - as everywhere.
- Ferry to Santorini: Easy to do, fun, a great way to arrive.
- Santorini: We stayed in Fira/Thira. Loved it. Thank you, travelerjan, for the recommendation for Stani restaurant. Absolutely amazing food. Ate there twice, and I had the lamb both times. Ended up at Rastoni's for our anniversary and the service there was impeccable and food wonderful as well, but at a different price point. We did the Fira-Oia hike, it was great to do but agree it's a bit of a hike (13km). The views are stunning though and water tastes pretty amazing once you are done...
No problems with flights or hotels or ... anything. This was such a wonderful trip and a complete surprise for my husband, which I was of course thrilled about. Thank you again everyone for your suggestions!

Glad everything worked out so well, thanks for coming back to tell us -- so many times we "vets" spend time spinning scenarios, yet don't learn what happened. But are you concerned that you've set a High Bar ! Next year for his Birthday, a nice cake and a party hat just won't cut it!! he he