A walk around Upper Kananaskis Lake is about 17.4 KM I think and about four hours of steady walking . . . and surprisingly mostly flattish. Very scenic and pleasant.
Abby walking around Upper K lake:
Above Upper Kananskis Lake is Rawlings Lake, where the area looks like this. Primo Grizzly country though. Don't worry, the dogs were leashed and I let them go for a sec to get the shot.:
Picklejar Lakes west of Longview, accessed via the Lineham Trail, is a nice 45 minutes or so with one pretty tough part. Then a series of roughly five lakes at varying altitudes to explore. Popular and nice hike.
Below Ruby and Pete on the way up to Picklejar:
Keeper and Abby descend to the first Pickejar:
Chester Lake down the Smith-Dorrien Trail is a very popular hike. About 50 minutes up and then other explorations from there.
Below, Chester Lake in Larch season:
You would probably walk the length of Barrier Lake in the time frame you specified, parking cars at each end. You might have to cross a couple of creeks. I've biked it and I've run the 18 km leg of the K100 back there and it seems there's always a few creeks to wade through. For your hike, steady walking and undulating.
Above Barrier Lake with Keeper:
West of Longview, walking up to Elbow Lake also leads you down Elbow Pass and you can walk for hours back there. Probably an out and back but scenic all the same. Tough little hike up to Elbow Lake but surprisingly flat after that.
Ruby in the Elbow Pass
West of Chain Lakes, a walk up to Hailstone Butte fire station is a fun diversion and very scenic. About one mile as the crow flies to the station but about an hour walk to get there. Ruby on the way down from the Fire Station:
On the opposite ridge from the Hailstone Butte fire station, is a very nice circular ridge walk that descends into the forest and then eventually back out onto the road. We go there quite a bit. Ruby up there a month ago.
Ptarmigan Cirque, at the top of the Highwood Pass, is a nice little hike/interpretive trail.
On the other side of the Highwood Pass, is this place . . . we hiked up past the trees in the distance and I think you can go further. In the deep snow, it really is many hours!!! Pete takes a break.
Coming down from Moose Mountain (below). The flat spot just below was a location shoot for the high camp portrayed in Brokeback Mountain. Its about one and a half hours to walk to that spot and then more to the top.
Summer walking along the shores of Chain Lakes. Just make sure you're not bothering the cows if they're around. You can walk a few hours one way and then back.
Probably other things . . . .
Cowperson