You need to let her know IN WRITING (certified w/return receipt) at LEAST 30 days in advance of your intent to more.
You should also be prepared to explain how said move benefits the children and that said move will not interfer with Mom's Parenting Time or if it does, what plans you have to make up for it.
You should also be prepard to move without the children if Mom objects to the move or maybe Dad can commute.