Take a look at this company. I have done their tour and I would recommend it for sightseeing and an overview of the islands. It is a budget tour, but all hotels and transportation are included. If you are looking for a romantic get away, it is not that.
Carol, I was going through the same decision process last year and as much as I like to cruise, I decided that a land tour was the best for me. I spent 2 weeks on the Islands the last week of April and the first week of May and was not sorry that I chose a land-based vacation. I did all of my hotel and interisland flight arrangements through Pleasant Holidays. Someone else gave you the link on this post so I won't repeat it. I did 3 islands, Maui, Kauai, and the Big Island of Hawaii. Prices through Pleasant are really good and you can choose among a variety of hotels on each island. Also a good reference site for tours is www.hawaii.com. Another great site is the one for the tourism board. The link to their main page is http://www.gohawaii.com/Default.aspx . From there, you can explore each of the islands.