Marriott does have 5th night free, so as long as you are averaging around 60k or less points per night for the room, you should be able to make that happen.
I almost never see Swan or Dolphin suites listed for points; I do regularly see Swan Reserve, though. A tip would be to book as soon as you find some dates/points that work but then KEEP CHECKING BACK. The points the room costs per night often will go down the closer you get to a stay. Using this strategy, if they go down you can cancel and rebook at the cheaper points price, and if they go up...well good thing you booked when you did!