HI,
I have taken VIA rail 4 times from Toronto to Vancouver. Great trip. Took each of three children on a mom and kid trip.
If you go in late june or july it will be light very late into the evening so that is good and in the dark you can often see the aurora.
This past year there were many 50%off deals so look for them.
I did upper berth and lower berth that I liked because in the day you are in open seating and can meet your neighbors. There are also one person, two person and (one ) three person bedroom.
Meals are included in sleeper class and were very good.
A stop for a day or two in Jasper can be great too.
VIA is cheaper than the Rockey mountaineer but you don't get to see all of the interior of BC because it is night.
Once I took VIA to Prince George and then took a day train through the interior to Vancouver. Amazingly different geography and you travel the interior.