My advice - schedule the Safari for whenever you feel comfortable scheduling it. I've been on it many times - never early in the morning (I'm on vacation so getting up at 6 AM is not going to happen) - but during the later morning, at high noon, in the afternoon, the last trip before it closes, in the rain, in the sun, in the chiller times.
I saw animals every single time. Animals don't go by times on a clock.