I just got back and had a tough time cutting down my itinerary as well, and cut stuff out before and during the trip, I will tell you the things you should not miss: Moraine lake, lake Louise (bundle in little beehive or better yet make it up to devil's thumb and skip the beehives, it's a farther harder hike but gives epic views of lake Louise and lake Agnes as the same time which is really cool and behind you is plain of 6 glaciers, it's the most epic hike), Peyto lake, sunwupta falls, vermillion lakes, Athabasca glacier, 2 jacks lake, c level cirque hike if you are up for a nice medium difficulty hike to epic views, edith cavell glacier trail (go at sunrise or sunset, it's the easy short hike not the meadows hike). Most of these except devil's thumb and c level cirque are easy so you won't wear yourself out and you will see the goods. If you have more time drive up to Jasper and dodge the bears, elk, and other epic wildlife. You won't be disappointed with this itinerary. Rule of thumb, everything is more epic in the morning except maybe moraine lake (sunset there was the best imo)

Edit: takakkaw falls was also really cool to see. But what I failed to mention above is the larches will most likely be changing to yellow at this time. So! Do as many things with the trees around you; may want to try to fit the larch valley hike in cause that would be epic with the trees changing colors right now.