I agree with Explorenorth's suggestion. As you will have travelled thru Yoho NP on the way out. Go back over the Monashees on Hwy6, stay at Mabel Lake or Burton (great campground) then take 31A to Kaslo and the the Balfour/Kootenay ferry and return via Cranbrook, visit Fort Steele, stay at Norbury, take 93/95 to Radium, sample the hot springs, stay at Redstreak and return via Kootenay NP Hwy93.
Might be a bit of a push to do in 8 days but a really good drive.
Good luck