That's going to be a hard sell on this sort of timeline. The distance between Banff and Jasper alone is about 4-5 hours on the icefield (accounting for all the stops you will want to make). It's the wrong way too, for someone heading to Vancouver, and a big drive around.
What I would do, personally, is stick to the program through the mountains. Maybe do the Tyrell museum and stay in Calgary that night. There's lots to do in Calgary, might I suggest Winsports Downhill Karting (which you can also do in the evening). Then if you stay on the west side of Calgary, you can get away in the morning with good time. Maybe book a shuttle to Lake Louise/Moraine for that morning (do it now), because you cant drive up there anymore. Do that and try to get to Kelowna for that evening. Then it's just a straight shot to Vancouver the next day.
Well you can technically drive to Lake Louise still, but best of luck. If (if) you win the lottery, you get to pay to park (and it's not cheap).