The safari is the Wildlife Discovery Excursion, inside Animal Kingdom. IPO will make your reservations, once you let them know when you want to go. It is an hour long tour, in a bus with a total of 14 people, stops frequently for great photo ops and information. I've done it twice, so I thought it was well worth it.
Really, it's with "a maximum of 14 people". Hopefully you'll get lucky. We went on Dec 15th for the 1pm tour and there were only 6 of us on the bus with the driver and zoologist!!!! It was unbelievable. We were able to move around and take great pictures from several different vantage points in the bus.
Our tour guide was Laura. Her mom was also a zoologist who worked with Joan Embry (San Diego zoo - often on with Johnny Carson). Laura was OUTSTANDING, so informative with great stories from both her work at Disney, her work in San Diego and trips she remembers from her childhood with her mother.
I'd highly recommend this to anyone staying club level.