Are you staying in Banff for the whole trip?
A really easy hike I'd suggest is Grassi Lakes trail... it's in Canmore but it's only about 20mins away from Banff. You access the trail by the Canmore Nordic Centre area. At one point of the trail it splits and you choose the easy route or difficult route. The difficult route isn't hard at all (just watch your footing), I only see seniors and people with strollers going up the easy route lol.. it took me about 45mins to get to the top and it was amazing!
You miss this view if you take the easy route...
But once you reach the top, this is what you see...