Why not just use a convertible seat that can rear-face and forward-face? If BA requires him to forward-face in the seat on the flight, it would still be a better option than lapchild or cares. He can sit in the convertible seat oriented forward-facing just for the flight. Then, when you get to Canada, rear-face him in the seat like you would at home. If you can find an equivalent to the Cosco Scenera over there, this would be an excellent choice while traveling. It's extremely lightweight and converts easily. If you have the Combi Coccoro over there, that's another good option. Very comfortable, too.