We had a blast on what we called our Retirement Victory Tour of Alaska trip, in 2014. We left the states on the early side, crossing the boarder and spending May 1st in Canada. A few campgrounds and businesses were not yet opened, as it was a bit early in the season. But never a problem finding a place to stop for the night.
We went up the East side of the Canadian Rockies to Dawson Creek to pick up the ALCAN. Then came down Cassier as we headed South, towards the end of August. (Had planned to stay to the third week or so of September. But our daughter was getting married at the end of September, and the DW wanted to spend the time with her in the final planning stages.)
I'd suggest reservations for:
-In Canada, Victoria Day weekend, or get to spot a few days early to stake it out
-Denali - Even the large campground just inside of the park was full when we were there. We stayed in Savage for 7 days, on the loop to the left as you go in, a few spots are facing 'The Mountain' and you can sit in your coach and get a glimpse if you are lucky to catch out from under the clouds. (We did!)
We then went further inside to Teklanika(SP?), nice drive into park.
-Fourth of the July weekend. We were in Seward for the Race Down The Mountain. We did not have reservations (we did for Homer, but decided to push on a bit early), but were able to dry camp in the Elementary School parking lot. One of the best times of our trip was watching the race and the following Fourth of July! (And of course the battle between the churches, for best foods
The rest of the time we just winged it, and all was good...
We were just too early too see much action on the bears feeding, saw many blacks and grizzlies on our trip. We were fortunate while in Denali, as we: Saw The Mountain, The Wolf, The Grizzly...
I'll second the ride up to the top of Salmon Glacier. (Due to our puppy being with us, and not wanting to board her, we did not do any glacier tours or flights. So Salmon was one of our best views. We also hiked up to Exit Glacier, in Valdez, and that was fun too. Valdez was cool, and some good fun watching the bears and eagles come graze at the hatchery!!
Go and have fun, take time to stop and rest from time to time and enjoy things. We were very impressed with the parks of Yukon and BC, as well as Alaska.
Other great resources on planning, besides here and the mentioned Escapees, is the RV Net forums. Sue T Nelson provides some great input, and some wonderful pictures. We also found great info on reading the previous years posts. Follow along on the 2015 postings, and contribute. But you might also get some great ideas by looking at the 2014 posting.
Have a blast. We'll be back, in 2017!!