TA: your planned trip sounds similar to our original plan. I am glad we skipped parts of it and spent (only) two nights in Honolulu and extended our stay on Maui to 5 nights. We decided that with the intra-island trips you would lose too much valuable time. Although the flights are short, you always need to take the waiting time, transfer to rental car, stuck in traffic, check into hotel etc into consideration. Plus you need to be aware that some (most?) resorts have a 11am check out time and if your intra-island flights leaves later in the afternoon, you are kind of stuck.

As for Maui, I can only recommend the Westin Villas one more time, great stay there and at the moment they are fairly slow and we got the nice upgrade. (Plus you have a full equipped kitchen and even washer and dryer, which can help save on the food bill, if you want to). If you have the SPG points, well worth it.

Another highlight I forgot to mention (and of course I got the tip on FT) was the Hula Pie desert at Kimo's (we actually had it at Leilani's at the Whaler's Village, but same ownership). Awesome!!

Oh, and another tip: If you need snorkel equipment (and if you don't stop at Costco and co) you are still better off if you rent it from a dive shop, rather than at the hotels. We paid $16 for two days for full equipment at the Maui dive shop @Whaler's village (vs $16 for one day at the Westin).