First, as Mr. Vker mentions, you can't break up the nights from a TP award. Marriott used to have a 7 night Hawaii "sampler" award that came with two 2-night awards plus one 3-night. You could use the 3 award certs at any 3 hotels you chose. But they discontinued that a few years back.

Now as to what you can do with your points, I'm not sure what is available, what you want in terms of a hotel, or if you have points in any other hotel chain that could be used. But one option is you could use 135K points for a $1K Marriott Cheques award. That would give you a lot of spending for "activities", meals and possibly even some of your nightly rates (if you are using "cash" instead of points for some nights). That would leave you with about 150K points for night awards. Marriott has Cat. 4, 5 and 6 hotels on Oahu and the Big Island. But I think Maui only has Cat. 6 hotels.

What I might do, would be to check out the best "cash" rates I can find for all the Marriott's on each of the islands and see if there is one (or more) that may have a really low rate (and maybe use some of my $1K in cheques to pay.) Also, you state that you arrive in Hilo very late on your first night. You might see if there is a really cheap hotel to be had for that first night somewhere and stay there for the night.

I would also look at is the MVCI properties. While your chances of finding available award nights at them probably isn't very good, its worth a check just to make sure. The studio room lock-off section of those is the same points as a Cat. 6 for most of them (Cat. 7 I think on Maui.) Also, you could use upgrade awards for 1, 2, or even 3 bedroom units should any of those actually turn up to be available (and you want/need the room.)

Are you planning on renting a car at any of the islands? Marriott does have some Hertz rental awards that may be an option for you as well. I think you can get a 3 day rental for as little as 25K points. That may be an option for your points as well.