Original Message:
Re: Differences between new Marriott Lahaina tower and Original villas (by Gregory B.):
Napili and Lahaina (towers/villas) are the newest buildings. The units were designed and built to be timeshare with full kitchen and washer/dryer in the unit.
The original building (Molokai, Lanai, Maui wings) was originally built as a Marriott hotel and the rooms were later converted to timeshare units. The units are very nice and spacious, but have only a kitchenette instead of a full kitchen (that's the biggest drawback of the original building for most folks).
If your father-in-law is offering you a honeymoon with his timeshare in the original building, I can confidently say that you will have a wonderful time. Don't worry about trying to change to the new towers/villas - that would be very difficult if not impossible. I actually prefer the original building over the new towers/villas for a number of reasons (as you can read above).
Go, stay in the original building, and have a great honeymoon. One suggestion: Request a room in the Molokai wing of the original building if possible - you will like that better.