Having lived on the Canadian Prairies for 18 years of my life and you only have six days basically when you get to Winnipeg just start driving on Highway #1 and keep driving till you get to Banff or at least Calgary. You wont see much anyway between Winnipeg and Calgary. Not that there isn't but if you have 6 days your best bet is to see the good stuff.
If you are in Calgary during Stampede I would check it out if you are into that sort of stuff. If you get a spot at Calaway Park they offer pancake breakfasts and free shuttle rides to stampede which is so helpful. plus there is a small amusement park. You have Six Flags, this would be more like Half a Flag. But it ours and I love the place both the park and the campground. You can also try Calgary West RV Park.
If not make reservations at Tunnel Mountain as soon as possible in Banff. Use your toad to checkout the town and the area around banff. Lake Louise campground is nice but yes it is noisy because of the trains. And do check out Lake Louise itself and if you have time take one of the teahouse hikes. The views are incredible and bring cash to buy snacks and drinks at the end of the trail.
Another option would be to stay in Golden BC as there are private campgrounds that offer 50 amp service. On your way stop at Spiral Tunnels ( a must if you like trains), Takkakawa Falls with your toad. Your MH will definately not make it. Continue on from Golden to Revelstoke (awesome scenery), Rodgers Pass is on the way. There are a few full service campgronds in this area but they do book up fast There is a KOA which isn't bad.
From Revelstoke you have two options. You could go to straight to Vancouver either using the Coquihalla Hwy(sp) or the Hwy 1. Hwy 1 is an awesome drive but it will be really slow going in your MH. It is a slow go through a very scenic canyon but has truck traffic and is two lans and quite curvy. Take the Coke if you are on a time line. Another option would be to go to Kelwona from Revelstoke and skip Vancouver and go directly into Washington from Kelwona. Kelowan is on Lake Okanogan and you can rent a boat for the afternoon and go skiing or just hangout on the lake and soak up the sun. Also there is an abundance of wineries in the Kelowna area. Lots of great golf courses here as well. Vancouver is nice but it is quite a big city which requires alot of time to get around and see the sights.
Its really too bad you are so pressed for time. No matter which way you go enjoy our country as much as we enjoy yours.:)