Yes it is difficult to get up around 1:30 to leave your condo to meet in Haiku at 3 a.m. And we were all a little groggy and cranky on the bus ride up the volcano. But this ended up being our favorite activity from our Hawaii trip. The staff was great - especially Billy who was our guide up the mountain. He was very entertaining - funny but also informative about the islands and all of the changes and risks to the ecosystem. We lucked out getting on his bus.
For the self-guided tour, they stop along the way and point out landmarks with flashlights on the way up so you can navigate down in the daylight. There are only about 5 turns, and even with the help we managed to take one wrong one - although as Billy said, in Hawaii you really can't get lost, you can only "get late". The sunrise itself was beautiful and we also had a full moon. It is cold but we all had several layers which we then removed as we were riding down. The first part of the ride down is exhilarating with the switchbacks and the amazing views. But even the rest of it, through the neighborhoods, was a lot of fun. And we would recommend stopping at T Komoda Bakery for donuts/pastries in Makawao before returning the bikes in Haiku.