Hey, I see you settled for the 35L as a wide angle. Glad to hear it is working OK. Enjoy the creative possibilities of a large aperture with a wide(r) angle
I use my 35L to shoot my son all the time. It has become my favorite lens. There is something quite magical about shooting with it at very large apertures. It will distort out certain body features sometimes depending on your angle though, which I happen to like personally as I think it adds some character. Your kid is very cute and shot is a great capture. You also seem to have a very sharp copy of this lens. Mine has quite a bit more vignetting then yours wide open (on a 5D).
It's really nice. I am also struggling between a 35L and a 24L to go with a full frame camera. They are quite similar in terms of weight and price. What about other aspects... A tough decision.
These lenses have been in the market for about 10 years, and I am afraid my expereince on 85L (Mk1) (Within 1 week after I bought my 85L, Canon announced the launch of 85L (Mk II) would happen again after I buy a 24L / 35L.
(although I got the recent Canon rebate price locked in 
A tough decision.