How about getting 6 tix into HNL, and then just buying the connecting tickets to Maui? You might have a much better shot at availability into Honolulu with the number of flights there each day.

Another option might be partner award travel on Aloha from the west coast, with a UA flight to the Aloha gateway. This might be worth asking about, too. Aloha flies from Oakland, and a quick check of their web site also shows SNA, BUR, and LAS. I don't know if UA will do this as award travel, so might be worth a call.

I had a similar situation trying to book 4 family members to Orlando a few years back, and ended up flying one person on a 4 flight itinerary to make award travel work. It does have its challenges sometimes.