I was in Banff for a couple days and it was awesome!!! The sights are unreal!!! I think it would be pretty hard to get it all in with a baby. The scenery is so majestic. I would not miss Peyto lake, Mistaya Canyon, Lake Louise, the Icefields. TakkkawFalls is actually the tallest falls in Canada (although Niagara Falls is much much wider).
One spot no one mentioned is Johnston Canyon. Its a beautiful trail with 2 tracks- the upper falls and lower falls. The view from the upper falls is much better but even the lower falls involves quite a bit of climbing. Definitely can't be done with a stroller and it would be very difficult with a baby carrier.
The spiral tunnels in yoho park are interesting stop if you have time. Due to the mountainous terrain, in order for a freight train to get to the next spot, it needs to cross over itself 4 times!
Lake emerald is a beautiful lake too. Rowboats, paddle boats and kayaks are avail at most lakes in the area. We went motor boating very far out/ don't remember the exact location. There are helicopter tours , atvs, and rafting for those looking for adventure.
There are gondolas in the lake Louise area and in Banff. I Would recommend the Banff gondola. You hike up to the mountain top once u get out of the gondola and the scenery is unreal up there.
The driving on its own is magnificent. The roads are pretty new- the highways were redone for the Calgary olympics. There's virtually no traffic- when cars stop you know there's wildlife on the road/ bears, wolves, mountain goats etc.