In 1986, we made our first long trip in a 20' Komfort lite travel trailer from Las Cruces up to Banff over to Victoria and then up toward Squamish\Horse Shoe Bay. It was the summer Victoria was having the Expo. The only campground we could find with an open spot was just short of Squamish. A private one, just opened, right on the sound or bay. I remember there is a very high water fall
just along the Hwy before you get to Squamish, one of the highest in Canada if not the highest. We went back by the area in 1997 but could not find a sign of the campground. On our way back down to Victoria, I believe I found the site of the campground. It was part of a golf course. There were some campgrounds still along the way, just not that one.
Sorry, I can not help you much. There are many nice provenical parks/campgrounds along the route from Jasper over to the BC area. We did not go beyond Squamish. Have a good trip.