This past summer, my daughter and I took our bikes on a train to Jasper and rode back to Vancouver. We did the trip over 18 days with 14 days of riding.
Our route was through the Rockies to Lake Louise, Hwy 1 to Golden and Salmon Arm, then through the Interior to Vernon, Kelowna, and Penticton, and then to Keremeos and through the Hope Princeton Hwy. From Hope we rode south of Hwy 1 passing close to Cultus Lake, through Abbotsford and Langley. See attached image (yellow dots indicate where we stayed overnight).
We rode as much as we could off of main highways whenever possible (not often) -- some stretches of Hwy 1 are quite scary -- the 10-15km stretch east of Golden was probably the worst although Hwy 1 from Sicamous to Salmon Arm also has a lot to be desired.
I don't think I'd recommend the Coquihalla Hwy as it would be brutal. Huge hills and nothing along the way but fast moving, high speed, noisy, high volume traffic. I can't see it being much fun. The Fraser Canyon may not be a great choice either as it's narrow in many places but the scenery would be better, there's much more along the route, and there is way less traffic than Hwy 5. Our route along Hwy 3 was a bit sketchy in places but it was interesting and for the most part, quite pleasurable. Unfortunately, whichever route you decide on will not be ideal but I think Hwy 3 is the best choice (and why we took it).
We stayed mostly in Provincial and Federal campsites along the way, a couple of nights on the side of the road (one night in a free forestry service campsite), a couple of nights with friends, and spent three nights and had great experiences using the website http://warmshowers.org
-- a site that lists people who let you stay at their homes (either in their homes or camping in their backyards).
I've been working on a website about our trip but it's not quite yet ready. If you have any questions, feel free to contact me.