In my past experience as both a traveller and an airline worker, prices will only go one way for Ontario March break trips, and that is up. DW is a teacher - March break is always when we head south.
Airlines use yield management software to adjust pricing over time. For Ontario break any trip from a local airport to a vacation destination will fill quickly so prices will never drop, only rise as the computers realize what people are willing to pay. Living in Ottawa, we have had better luck flying from Montreal (different break dates) or through an intermediary airport (Cabo San Lucas via Calgary) to get on flights with (somewhat) lower demand.
You have the right idea driving. It's probably been 4 years since we have flown south, and there have been at least 6 drives to Florida or the Carolinas for us. Painless and a MUCH less expensive option at the break. Although be prepared for some potential weather. We missed most of the bombogenesis storm last March through planning and making an earlier than planned start, but still managed to catch enough of it to do this: