I was fortunate enough to already have a closed rack, and our daughter (2 1/2 years old next month) has just been strong enough to open the door for a few months now. Fortunately she doesn't often open it. I was also able to keep her clear of the wiring with a couple good-sized barricades (LFM-1 on the right, large glass jar of change on the left). Is the rack tall enough that you can move the components with controls up out of their reach? It's a short-term solution (they do grow fast), but might get you to the point where they can learn to leave it alone.

The first time Kate opened the cabinet and grabbed the 990's volume knob, I wondered about a firmware change that would disable the front panel but never asked Outlaw about it...