Hi from another Hawaii
DVC owner with a similar family structure ... it is me, DH, and our DS4. We bought VGC because we go there every year, and we usually meet up with friends so we get a 1 or 2 bedroom. We have not had success with getting rooms for extra nights past the 7 month mark. For us we will be going to the Land every year anyways, usually combined with a trip to see friends and family on the mainland so airfare was something we were accustomed to. If you want to stay at a few resorts: BLT, VGC, BCV, it does that one needs to own there and book early! (I like to make my reservations with some 'room for error' then buy plane tickets a few days before/after [whatever works and is reasonably priced within our time-off from work] then we stay offsite or DLH for the first/last few nights, head down to San Diego or up to Magic Mountain, etc.)
Unfortunately VGC is sold out right now with a waiting list and those who have been trying to buy contracts have been getting ROFR'ed so if VGC points are what you want, its probably a good idea to get on the waiting list soon ...
Also, just a side note ... Aulani is a large resort that has much higher MF's than VGC, so you'll also be saving some $$ there by buying in Cali or WDW as opposed to closer to home ...