(1) An uncooperative four year old daughter (mix of low light shots at home and shots outdoors)
135mm f/2.0L 85mm f/1.8 50mm f/1.4 35mm f/1.4L
(2) Cityscapes and architecture (Live in Chicago, so lots of great places to shoot)
TS-E 24mm II (I love mine...) *The advantage is that you will not have to save for this later on*
The TS-E 45mm is an old version and probably due for update...
(3) Sunrises of the lakefront (Live very close to Lake Michigan facing east with unobstructed view from my balcony to try to capture some great sunrises)
Range from Ultra Wide to tele...
(4) Prairie landscapes (embracing the flatness of my home state)
Wide Angle 16-35mm f/2.8 II or TS-E 24mm (best Canon 24mm probably...) No need for 1.4
(5) Museums like the Shedd Aquarium which currently has a great temporary Jellyfish exhibition
IS could be helpful here or a very fast lens, however you do need some DOF
so 24-105L IS (although agreed, it is not so fast), 50mm f/1.4
Let me say however that you will find the 70-200mm f/4L IS very good and very portable.
Its Image Stabilization is exceptional too.
I hope I didn't confuse you with so many suggestions...