You are quite right that the 3-in-1 isn't going to work for your daughter right now. It should be a good RF seat for the new baby in a bit though.
I'd look at getting a Graco Nautilus. It harnesses to 65 pounds, then becomes a highback booster, then a backless booster. It should be the last seat she needs, and you should be able to find it in your price range, even in Canada.