Carol,

Generally the animals are laying down and not too active - just like housecats. So you will have pleanty of time for manual focus. But at least with a D70 you will know if the autofocus buggers you.

Remember also part of the show is the very different night sky.

One other important tip. Before morning drives they generally will offer up tea/coffee. Take a pass, as there will be no restroom breaks for about 3 hours.