You can only book sunrise safari if you are staying in the concierge level. That can be booked right through the concierge person at AKV 180 days out. The sunset safari can be booked the same way, only you don't have to be staying concierge to do that one.
For members, the sunrise is $55 and the sunset is $160. There is that $5 discount for the sunrise, but no discount for the sunset.