Denali is very strictly regulated due to the fragile nature of the environment there. You have to take the bus, at least past a certain point, as far as I recall, and that point is way before almost anything worth seeing.
The buses can fill up days in advance. I was last at the park in 1999 but I would imagine even in the days of cell phone apps you probably have to be at the park to sign up for seats and cannot do it remotely, though you might want to check with the Park Service to verify.
If you intend to hike at all you are required to watch a video on grizzly encounters--and the park is full of grizzly bears. Earlier in the summer they might not be at lower altitudes but later in the summer, when I was there, they come down to lower elevations to gorge on berries for the winter, so you see them constantly out of the bus windows, just off the road.
I was lucky when I went to Denali. The weather was bad when I arrived, so I signed up for a slot on the bus for 3 days down the road, went to Fairbanks for a few days, and then came back in time for a rare clearing of the weather. The view of McKinley was FANTASTIC and I rode the bus all the way to the end of the road. But what I saw with the clear weather is that Denali is not an easy or great place to hike from the main road. You are on one side of a large, flat, treeless valley. If you climb the hills to your north (just above the perilously high road you are riding on in a school bus) you might get a better view but they don't go very high above you so I don't think there's much to do there. If you want to hike towards the Alaska Range you will simply be plunging down into a giant valley filled with grizzly bears and it's a long, trail-less distance to the mountains, more than a day's hike. There are small hikes closer to the entrance of the park but you won't see McKinley or the other snow-covered peaks of the Alaska Range. It actually takes quite a bit of time on the road to get to the point where you can even see them. It's a very big park.