People would be lying to you. It's becoming nearly impossible to get a job in many Canadian provinces if you aren't bilingual.
I speak quite a bit of French and struggled to find a job because my French wasn't good enough for multiple places. Including FAST FOOD. (This was right after high school lol)
I think this is 100% true for Eastern Canada but here in the West (lol) you only need French to work for the government or to teach French.
I would recommend teaching your children ASL, I know a lot of it and will continue to learn it until I'm 'fluent.' It is invaluable.
If your kids are going to learn both anyway I would probably suggest going with Spanish for the aforementioned practicality. Especially since it would be easier to find people to practice with them.
I am personally partial to French but I'm trying to leave that bias out. French is great if you plan on working in governments and not just Canada's. A lot of organizations have French & English as their official languages.