I'd suggest giving some non-internet aided thought to what you want to see, both in the Continental U.S. and in Canada: is it historical places to stop? Scenic vistas? As many miles as you can travel in a day? Endles fields of grain? Mountains?
Once you've got a sense of your "wants to see", that might help determine your route. In 2009, although I didn't drive the Alcan, I was in the midst of moving and drove from Ewe-stun to Seattle where I put my P/U on AVT and flew to Los Anchorage.
That 2009 trip was after living in the Houston area for 7? 8? years and I was desparate for vertical relief so my route to Seattle was: Ewe-stun - Albuqurque - Durango CO - Grand Canyon - Flagstaff - Idaho - Oregon - Cascades - Seattle....long and very indirect but it got me my mountain fix.
Determine what parts of the country you want to see and then plan your route. I'd suggest (whether you use Google maps, Mapquest, etc) that you only use the software to plan any given leg and that you define the overall route based on your preferences.
...and as stated above, take the driving times listed with a grain of salt.