If it's anything like Toronto Pearson International Airport it's a crapshoot.

Step 0: With kids, corralling the children takes a while and can be like herding cats.

Step 1: Just getting to the airport, from 40km away if you are driving/Taxi, it will take from 20 minutes or 2 hours+ to get to the airport. People who use YYZ often live further than that so add any additional time from that. The Union Pearson Express train is only useful if you are trying to get from Union to Pearson or somewhere between. The 900 bus from Kipling, local TTC routes, Go Bus, MiWay, Brampton Transit all feel second class and you get the same rush hour traffic.

Step 2: Check-in. Domestic flights are fine because not as many people check bags and the counter is quick or you can often skip it entirely. International flights have long, long lines at the counter so add an hour.

Step 3: Security. Another crapshoot depending on whether you are there at peak time. Could be 5 minutes, could be an hour or more to get through.

Step 4: Attending to food and washroom needs. Since it's not possible to know exactly how long this process will go, if unprepared, random food and bathroom stops may be necessary.

So all in all preparing for the worst by leaving/preparing to go at 6:30 for a 14:00 flight is not unheard of when flying via Pearson.