I look at it slightly differently. I think going somewhere neither of you have been , and experiencing it together for the first time( sort of like losing virginity, LOL) is a special way of ensuring you will share memories of this honeymoon as being unique to this specail time in your lives.
I have done Europe many times, and I love France and Switzerland best, but, I have to say, at your age, I think a trip to the islands of Greece WOULD be my choice. I loved loved loved Greece. It is very romantic. And so beautiful I have been in late Septand the weather is still wonderful for finding a secluded beach and just relaxing and clubbing at night is fun too..try Santorini, Mykonos, or a
quieter chice might be Paros.
I have kept this hotel on my favorites for years, I have not been , but the reviews are good on this place, and well , just LOOK at that view.
It is Hotel Tagoo in Mykonos.
http://www.hoteltagoo.gr/
Good luck.