i'm planning my first ALON in June (God willing that United is still around!), so i THINK i can answer a few:

1. i think you could stay at basically any other hotel in the hilton "family" (if there are any in Hawaii), although probably a waste of 100k points, since they aren't resorts.

2. i think you can book only 1 year in advance, although the HWV is so big, you probably have some leeway. but, there is no real downside. make your reservation ASAP using your points (assuming you already have them). you don't have to request the actual certificate until you get close to the travel date. this allows, you can modify your reservation or cancel, as the certificate is not printed to be used for specific dates. and even if you do request your ALON certificate, you can always send it in and get the points added back to your account fee free.

two caveats: 1) there's no telling when/if Hilton will change the points required for the ALON (especially since cheapos like me can earn 100k without staying at a Hilton, period). requesting the certificate now "locks in" your ability to use it, 2) however, you have 1 year to use the certificate, so don't ask for one TOO fast (although you could always send it in and get it "recommisioned", that could take a few months).

3) if i were you, i'd go ahead and do the point thing at the same time you ask for the ALON. that way, you're covered, but can still cancel it later if you see a good last-minute deal, then send in that certifcate to redeposit in your account.