Along the river in Banff is a really nice place to walk with a stroller. The Banff Gondola is a great activity for families, the view from the top is incredible and there is a brand new interactive center up there. Kids under 5 go free. The museums are really fun for kids as there are lots of hands on exhibitions and furs/antlers to feel. There is the Cave and Basin, the Buffalo Nations Luxton Museum, The Whyte Museum and the Parks Museum.
Thanks so much!