I would say no. They hold you at Discovery Island, but it's still a 5-10 minute walk to the safari and then you have to wait and I think the ride itself is at least 15-20 minutes maybe more depending on the animals.
I would move the reservation to either prepark opening or to later in the morning, say 10:45, which is what we did and that's perfect for us.
Enough time to ride the safari, walk the trails or ride the train to Rafiki's planet watch.