Try this page at allearsnet for some details on both safaris.
Here's a quick summary:
The Sunrise Safari is offered on Saturday and Tuesday mornings, and takes place in the Kilimanjaro Safaris area at AK. I believe the current cost is approx $50 for adults, approx $30 for children. It includes a meal at the Tusker House.
The Sunset Safari takes place on the grounds of the AKLodge, is limited to 8 guests at a time, includes dinner, and the cost is $150 and guests must be 16 or older.
Both Safaris are available only to Concierge guests.