RV roadtrip to Glacier, Yellowstone and Grand Teton NPs (from/to Calgary)

I would suggest choosing Option B because it appears to provide a more even schedule with less time spent driving, which should be better when traveling with children. When you visit Grand Teton, think about staying at Colter Bay Campground; it is good for families and the views are very beautiful. When you travel from West Glacier to North Yellowstone, it might be good to stay in Missoula on the way. This town is pleasant and has places that are suitable for families. While returning to Calgary, consider visiting Waterton Lakes National Park; it is very beautiful and has excellent hiking trails that are appropriate for children. Have a pleasant journey!

The 'obvious' route that most software will probably recommend is simply US-93 to Missoula, I-90 to Livingston, and US-89 to Gardiner. However, the route is well short of 400 miles which means that you'll have a little time to take a slightly more scenic route and get away from the truck traffic on the Interstate. What I'd suggest is US-2 to Evergreen, MT 206/MT-35 to Bigfork, MT-83 to Clearwater, MT-200/MT-141 to Avon, US-12 through Helena, to US-89 south to Gardiner. Helena would be roughly halfway, but with the RV you should look at Cromwell Dixon Campground.

AZBuck