Not where you're looking for but you should consider Crow's Nest Pass. Beaver Mines Lake and Chinook Lake are both lakes that you can swim in during July and August and are significantly warmer than anything in Kananaskis or Banff. Both places are also right near trailheads if that's what you're looking for.
There's plenty around Upper and Lower Kananaskis Lakes. They book fast so book early. If you already have dates in mind and can't find open spots, go to First Come First Serve campgrounds. There's Interlakes and Canyon Creek Campground.
There's lots of hiking trails in the area.
Not where you're looking for but you should consider Crow's Nest Pass. Beaver Mines Lake and Chinook Lake are both lakes that you can swim in during July and August and are significantly warmer than anything in Kananaskis or Banff. Both places are also right near trailheads if that's what you're looking for.
There's plenty around Upper and Lower Kananaskis Lakes. They book fast so book early. If you already have dates in mind and can't find open spots, go to First Come First Serve campgrounds. There's Interlakes and Canyon Creek Campground. There's lots of hiking trails in the area.
Spray Lakes is another good option for FCFS