I would switch Day 5, 6 and 7 around.

From Revelstoke, I would drive to Banff. It is not far - 3 Hours max. Do your Banff Activities. Then, head West, back to Lake Louise, do your Lake Louise activities, and then head North on the Colombia Icefields Parkway, one of the most beautiful drives in the world ending up in Jasper. Then drive Jasper to Kelowna (Same distance as Calgary to Kelowna). I would honestly skip Calgary (I live here - sorry calgary). If I gave 10 people your option or mine, I bet 9 would choose mine. It's that beautiful.

I forgot to take out Calgary. I have edited my previous post. We are going to stay an extra day in Seattle to be with relatives.

I would still suggest looping through Jasper on your way back West rather than backtracking on the same highway

I think you are rushing through the mountains. You have a day of hiking in Banff but not in Jasper. Each park warrants more time, in my opinion, minimally another day each. If it were me, I'd ditch Seattle in favor of more time in the Rockies.

Seattle was originally not part of the plan. But when the relatives learned we're going to NA, they asked that we should meet with them for a couple of days. Cannot say no to them.

If you can squeeze in an additional day in Banff, you will not regret it.

I know. I would have stayed 2 more nights in Banff and 1 night in Calgary, but we were obliged to go to Seattle.

To make you feel better, I will tell you that Seattle is a lovely city. Get out on the water.

I've been to Seattle before. It's a quiet city, somewhat like Vancouver.

Anyway, I'm not going to worry on our itinerary in Seattle as the relatives will take care of it.

Be sure to check drivebc.ca to find out the road conditions on the routes you will be taking. It has all the information about construction, accidents, and any other reason for the road to be closed. What might look like a nice 5 or 6 hour drive could take a day or more if the road is closed for a land slide or bad traffic accident. Drivebc.ca also has a twitter feed which is very handy for up to the minute road reports.
Have a great trip. I think your itinerary looks great.Can I come along?

From Kelowna, we'll be heading to Seattle. Which border crossing should I take, Osoyoos or Sumas?

The route through Sumas is faster (and the border is not *usually* congested there in contrast to Blaine), but the WA-20 route through Washington Pass is more scenic.

How about Sumas vs Osoyoos?

That's what I meant by 'WA-20 route': BC-97 to the border in Osoyoos, US97 to WA-20 over the mountains.