Visiting Hawaii in August for the first time with my wife and 2 daughters, ages 11 and 14. We'll have 14 days in paradise, plus 3 days in addition for travel. I'm not sure if it's wise to try and fit in more than two islands, which is tough because I don't know how to make choices between Kuai, Maui and Big Island. I also figure that at least a few days in Oahu are unavoidable. We are not the rugged hiking or scuba diving type, but will swim (beach and pool), snorkel, walk around, and want both the lush beauty and volcanic impact. We all love to eat, my daughters and wife like to visit unusual stores, but I wish to generally avoid prolonged stays in congested areas. My only concerns with Big Island are forcing my sometimes impatient daughters to spend too much time in the car driving around, and whether my wife's very slight asthma condition will be aggravated by the sulfuric air near the volcano. If for one of these reasons we couldn't visit the volcano park, would Big Island still be worth one-third/one-half of our vacation time vis-a-vis Kauai/Maui? The reason I figure we'd do a few days in Omaha is because it's likely we'd be flying there from the mainland and would probably want to give my kids a break from the travel. Would appreciate hearing if that's a valid concern.
Any and all advice appreciated!!