Joanna, thanks for asking about Hawaii - we had a great time. The weather was perfect (low to mid 80's, low humidty, nice breeze), the resorts were beautiful, and the kids really enjoyed it.
My MIL and FIL were along to help with the kids as we had to spend a good chunk of time at a business convention. I was worried they would drive me crazy but it wasn't too bad. I tried to do a lot of preplanning for them and gave MIL all kinds of info and recommendations but they were hesitant to plan too much. All I could do is shake my head when MIL and FIL spent one afternoon they had fre without the kids driving 40 minutes each way down to Kona so MIL could get her film developed at Wal-Mart (one hour processing!) and have lunch at McDonald's! They must have gone to that Wal-Mart 3 times during the 10 days they were there. They flew back with the kids as we moved to Maui for the 2nd part of the convention. Their flight back didn't leave until 9pm and they didn't know what to do to kill time. So they took the kids to a movie and then the mall. I guess that got me the most upset because there was so much they could have done that last day - that's why we booked a late flight for them!
Overall, though, it was a great time. DW received an award during the convention and now we get to go to Pasadena for the Rose Bowl parade on New Years Eve. DW even gets to ride in a float! Best part is the kids are welcome this time - we don't have to hide them with MIL and FIL like in Hawaii.