Thanks for the info and route suggestions. Whats hwy5 like?
Like you mention, Hwy99 to Whistler looks good. Then get back on hwy5 to Jasper. Would you pick this over hwy7,5?
Hwy 5 is the fastest route, starts off with evergreen forest and has a long steep climb we call the Bear Shed. There's a rest stop at the top with a nice mountain view. Heading toward Merritt (good idea to stop for gas and/or food here) and Kamloops, where it's drier, you'll see more valleys with ranches. The road is wide with 2 or 3 lanes per direction to pass the big rigs that frequently take this route. Past Hope this route has been fairly quiet and relaxed whenever I've driven it. The worthwhile sights I know of are Othello Tunnels and Hell's Gate (actually up hwy 1 a bit from Hope, but you could take the detour and come back).
Hwy 99 would be my pick, but I've been to Othello and Hell's Gate a few times already. Check google maps and the radio traffic report before starting in case there's a major collision on the 99, or you could be stuck for hours.
The 99 is twistier, but has a lower speed limit until past Squamish. It switches between 1 and 2 lanes per direction and hugs the coast from Vancouver to Squamish, so the distracting views can be very good, then goes inland toward Whistler. There are a number of scenic rest stops with signage, as well as lakes and waterfalls. If you don't go early in the morning it can be busy, with a mix of people driving less than the limit and impatient tailgaters asking for a tow by the popo. In Squamish is The Chief, which is a nice hike (or climb) up a granite dome with a great view of the town from the top. I stop for gas in town because it's cheaper and I can get either Shell V-Power or Chevron 94 instead of the ethanol blend. Traffic tends to thin out past Squamish, but hwy 5 still seems quieter. Whistler has great restaurants, and you can hike up the mountains, or take the gondola up and just hike around at the top. There are guides if you want to do something technical. I would expect it to be quieter past Whistler, and Duffey Lake Rd (still hwy 99) is a great drive.
Either way, when you get to Kamloops, there was a restaurant at Hotel 540 on Victoria st that had good pancakes with a bit of crispy caramelization on the outside. This is of course the most important bit of info I have for you