On Day 6, stop and pick up a picnic lunch and then drive back down the Icefields Parkway and stay in either Lake Louise or Banff that evening. We did this exact trip without the Stampede in Sept 2008. If you click on my name you will find my trip report.

I personally would not do the tour even though your parents are 78. They won't want to hike to Lake Agnes but they would enjoy walking around Lake Louise and Moraine Lake and they should be able to make the short uphill climb to the top of the rockpile at Moraine for the beautiful view.

I would just drive around the area. There are so many beautiful views right from the road and the driving is not difficult. You can drive to Lake Louise, see the lake, drive out to Moraine Lake, walk around, then drive out to Emerald Lake Lodge for lunch, stop at Takakkaw Falls, pass the spiral tunnel on the way back to Banff. If this area really interests you, perhaps you could stay the first 2 days in Lake Louise and then spend the evening of Day 6 in Banff.

If I had to choose between the 2 Fairmonts, I would choose the Banff Springs. The Chateau has never appealed to me--but I have never stayed at either. We always make a stop at the Banff Springs though---I love that place.

If you are considering the hike to the Tea House, I would definitely recommend it. We did the hike with my parents, who were in their late 60s, and my children who were about 6 and 8. While it is a long hike, the views are worth it, and you can stop at the tea house and have lunch or a snack. We have never stayed at the Fairmonts, but have eaten lunch at them and wandered around the shops and lobby. If your parents didn't want to do the hike, I think they could walk around Lake Louise and spend time in the hotel and on the grounds, while you are hiking.