J.B.
Check out www.vrbo.com. I use them for EVERY vacation! I've never been disappointed either. Because you rent through the owner and not an agency or realtor, you get cheaper rates and you can also see traveler reviews, photos, etc. It's nice to be able to contact the actual owner as well if you have any special considerations or needs and sometimes they'll work out a payment plan with you. They have great deals on VRBO for Hawaiian islands! They list townhomes, condos, apartments and homes.
It's been awhile since I did Oahu and Honolulu, but the bus service there used to be fantastic and it was super cheap! Read some current guide info about it to see if it's still an advised mode of travel. Two things to see in Honolulu -The Polynesian Cultural Center and The Honolulu Zoo -especially if you have little ones.