After looking through your thread, I think your wife is absolutely correct. You will regret selling the Hasselblad.
I have a 3 year old boy, and another one on the way.
Are you finding it so much easier to photograph your son with your Russian 35mm rangefinders compared to the Hasselblad?
I actually find it much harder to photograph my son with my Leica M7. Trying to center the eyes on the RF patch, then getting accurate focus is an exercise in frustration. You end up pre-focusing, and hoping that he runs into the focus zone at the same time that the shutter fires. This is actually easier seen on the screen of an SLR. That's why I've kept my Nikon F3 (besides its intrinsic greatness as a camera). It is actually easier to do it with a TLR - hence my Rolleiflex. I don't see why you can't do the same with your Hasselblad. Anyway, focusing an M Leica will be no easier than focusing your Russian RF cameras.
Yes, Leica lenses are great. I have the 35mm Summicron ASPH, the 50mm Summicron (pre-ASPH, i.e. the current version before the new $7K one was announced). While they are some of the sharpest lenses in the world, the end result is that they image on a 24x36mm piece of film. When you compare the results to medium format, they still aren't comparable. The images from your Hasselblad are going to win every time. My Rolleiflex produces better images (at least on a technical basis), than any 35mm camera, even Leica.
The ideal solution for rapid pictures of your son, is an auto-focus motorized 35mm SLR such as the Nikon F5 or F6, or the ubiquitous digital SLR.