I just Stayed at Waikoloa Marriott Resort and Spa on the Big Island Hawaii.(Love it)
Book both rooms through Vacations By Marriott. Iam told I can't get the rooms as Elite nights but I did get points. One was book for 8 nights the other for 9 nights.
If this is because they classify Vaction By MARRIOTT as a third party then they need to tell people. I was misled to believe that these reservations would qualify as Elite nights.
After all ,Vactions By marriott is found right on the rewards web page!
Here's a recent post that probably answers your question.
The following is from the link I referred to. Seems to me this covers it.
"Elite night credit is only given for the room occupied by the member. Points are earned for all three rooms and if the rooms were all charged to you the points for the room charges should have been credited.
It can be confusing when the Terms and Conditions of the Marriott program say that you can get credit for up to three rooms. Unfortunately, that credit is limited to the points earned. Only the room occupied by the MR member is credited as an elite night."