Ditto on Alaskan Highway in early spring for animals. We saw more wildlife on the highway than we did during our two summers of 4 months each.
While on your loop spend a week at Teklanika in Denali and ride the first shuttle bus each morning. You will see a lot of wildlife!
Take a sightseeing cruise out of Seward for sea life.
Go for a cruise on the Lulu-belle out of Valdez for whales and glacier vews.
That should take three weeks and whet your appetite to come back and spend the summer when you are able.