I don't think you will drive 300÷ miles a day and enjoy your trip. We arrived in Tok on Aug 1. We accessed the Alcan via the Cassier Hwy. From blogs and talking with friends we thought the Cassier would be our worst driving, it was not. We drove from Whitehorse to Border City, about 350 miles and it took us over 10 hours. The bad roads and construction were the worst the last several miles. This isn't to discourage but so you will be prepared. Had we realized how slow we would have to drive we would not have attempted the drive in one day! Unfortunately after we got to the borders there was no place to stop. When we got to Border City we should have stopped but the roads were good so we decided we could make it to Tok only to have more construction. We found a nice pullout and spent the night because we were so tired and drove to Tok the next morning.
All that to say, plan on slow going and about 200 miles a day. Don't push it so you can enjoy it!
Thanks for the question about Denali. We will be headed there in a week or so and I was wondering if we would need reservations. Sounds like it is a good time to go!!
Hope you enjoy your trip! We certainly have and learned alot from all these bloggers!