If you can afford to do Hawaii, I would say do it!
We went again this past March to Maui with the entire family. (grandparents, husband, sister, brother in law and three kids 11,9,5) All everyone talks about is when are we going again and we are all, well almost all,
Disneyland addicts.

My daughter's first trip was when she was 5 and she had a great time, we've been back twice since then and hoping to go to the North Shore of Oahu next year.
We love Disneyland and we will make it there later this year but that is a short vacation that we can work in but Hawaii is a BIG vacation and if you are able to go with the crazy airfares and all, I would do it. You will not regret it. It is totally a different vacation that a Disney vacation. I love them both but if I were to choose it would be Hawaii, Disney is much easier to get to at least for us.
Do you know what island you are planning to visit? If you have any question or would like some help planning, just PM me.