Why not?
Kids are mobile. Mortgages can be covered by tenants or by selling the property (usually).
I only have kid (singular) and lack a mortgage, but I'd definitely move my family to a place with more opportunity if the well ran dry where we're at now. I wouldn't even hesitate or think twice about it. The temporary pain of transition is going to be a lot easier than the long-tail of fruitless toiling and economic decay.