There's a group of operations staff in an office building across from YYZ that controls the whole system (and AC Express's). They ensure there are aircraft and crew to cover off the schedule, and when operations are impacted by weather or mechanical delays, factor in the variables and make the decisions.

As for the OP's contention that because the vouchers he received appeared to contradict the weather rationale, remember these things are boiler plated and because AC was good enough to offer them, he now believes this changes the voracity of this rationale and the issues that cascaded to his relatively minor 3-hour delay.

As for taking care of an infant for those three hours, nobody told him to travel with a child nor even procreate to have one to content with. Own up to your own responsibilities as a parent and don't blame the airline for a relatively minor delay on a once-a-day flight that had been impacted by winter storms that played havoc with the Christmas schedules of all airlines operating in eastern NAmerica.