We booked the Pearl Harbor VIP military base tour through Celebrity. The tour guide was excellent. We were on a 22 passenger bus/van. The tour company is called Home of the Brave Tours. I highly recommend them.
This is a VERY long tour that takes you all the way up and back on the Road to Hana. We had a very good tour guide who told us lots of information about Maui, plant life, Hana. The tour company (booked through Celebrity) was Polynesian Tours (I think) and we were on a 22 passenger bus/van same as the Oahu tour.
Take a motion sickness pill before you go - the road is very curvy.