I wouldn't recommend going to another island for a day trip in Hawaii. The airports are on the opposite side of the islands' attractions (because who wants a jet flying through their resort view), so by the time you get to the airport, take the flight, get to the attraction, half your day is gone. If you want to see the Volcano National Park, just tack a day or two onto the end of your trip to go to the Big Island, then fly home from there. Or beginning of your trip in reverse.
Day tripping to other islands is only something I do if I have to for work or a test or grad school. Really not a great way to spend a vacation, and airfare between the islands is really expensive now that one of the two major airlines went out of business a few years ago.
