Good advice.

Dublin to Belfast is a pleasant trip on the train, too.

You can purchase one-way Enterprise train tickets for 14.99 EUR per person several weeks before travel (about 21.50 CAD).

Take a taxi from the airport to Dublin Connolly railway station (you will also see it signposted as "Stáisiún Uí Conghaile" or just "Conghaile", don't worry, it's the same place).

The UK/Ireland border is all but invisible, even for non Irish/British passport holders. There is no check in requirement and no rigorous document checking at the station, but keep your passports handy just in case they check you before you board.

It's a little over two hours to Belfast and the journey is comfortable even in Standard Class (Irish railways have a slightly wider track gauge than Canadian or British railways, which gives a little more space inside the train too).

At Belfast Central, you can take a black cab (just like the London ones) to Belfast City Airport which is just three miles away.

Alternatively, if you want, you can make a stop overnight in Belfast. I would recommend this if you have the time. Belfast is quite forward-looking these days and there is plenty to do, ranging from a browse of the shiny new Titanic Quarter to taking a guided tour of the political murals of the city.

Belfast City airport is small but perfectly formed - one of my favourites.