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I went last year for 2 weeks - Wrangel -> Juneau -> Anchorage -> Fairbanks -> Denali -> Seward -> Homer.
Fairbanks was unremarkable. I would skip it if we went back, personally. There was not much to see, and most of it seemed like a tourist trap. There was a nice model railroad at the train station. That was pretty much the best thing that we saw in Fairbanks.
Denali was spectacular. We stayed at a lodge in the park. I'm sure that you've read about how the park works -- you can't drive very far into the park itself, you have to use the buses. The mountain is unbelievable. My wife pointed it out to me on the bus, and I was amazed -- but then I realized that I was looking at some other mountain under the clouds, and the real peak was poking out OVER the clouds. It was incredible. The mountain can be tough to get good pictures of, though, because you can only see it clearly when the weather is nice. We didn't have a really clear view of the mountain until our last day there (we stayed for 3 days), and that was on the bus ride back. Below is a picture that we took of it -- through the window of a moving bus, if you can believe it.
We didn't spend a lot of time in Seward. My wife didn't like the town very much, although it may have been the weather. I liked it just fine. The wildlife center there is great. We went late in the day and had the place to ourselves, pretty much. They have only real Alaskan wildlife, and it was great to see the stuff that we had been seeing in the wild up close. But the two things I remember most were (1) the "touch the anemone" exhibit, which was really cool (they had a guide there who explained what everything was, and you could touch all kinds of Alaskan sea life), and (2) the bird room. The bird room was really fun for taking bird-in-flight pics. Sure, it is kind of cheating, I guess, but I didn't care. My wife and I spent about an hour in there taking pictures of the birds flying right by our heads, jumping in the water, diving, fighting, etc. It was great. I think that a 70-200 is good enough to get some great bird-in-flight shots in that room if you are so inclined. They also have a room below where you can watch them diving into the water and swimming around.
In Seward we also did a wildlife tour, which was also excellent. Here is the group that we used:
Alaska Saltwater Lodge
"Small Group Whale Watching, Wildlife & Glacier Tour," lunch included, $199 per person.
The non-Denali pics below are from this wildlife trip. We saw tons of puffins, some other birds, lots of eagles, sea lions, sea otters, and lots of whales (orcas and humpbacks). We also saw ice breaking off from a glacier, which was so cool looking that I totally forgot to take a photo of it. Overall, it was well worth the $400, even though it rained the whole time. I would definitely bring a rain cover for your camera, and if you are going in late August like us, some jackets (my wife was cold the whole time in Seward). On the wildlife trip, I mainly used a 300 f/4 on a D600 (full frame) or a D7100 (crop) with a 1.7x TC, and I never felt desperate for more reach (although an extra stop or two wouldn't have hurt).
Edit: Homer is well worth a stop if you happen to be nearby on a day with a very low tide (look for at least -4, ideally -5+, if I remember correctly). They have some amazing tidepooling trips -- you basically just walk around and look at all of the sea creatures (Octopi, starfish, clams, crabs, etc.) that unexpectedly end up out of the water at low tide. They also have a great little town called Halibut Cove that you can take a boat to, with a decent restaurant.
NIKON D600 50.0 mm f/1.8 lens 50mm f/5.6 1/4000s 360 ISO -1.0 EV
NIKON D7100 300.0 mm f/4.0 lens 500mm f/8.0 1/3200s 500 ISO -1.3 EV
NIKON D7100 300.0 mm f/4.0 lens 500mm f/8.0 1/640s 800 ISO -2.0 EV
NIKON D7100 300.0 mm f/4.0 lens 500mm f/8.0 1/320s 800 ISO -1.7 EV
NIKON D7100 300.0 mm f/4.0 lens 500mm f/6.7 1/500s 800 ISO -1.3 EV