One is "required" to comply with the custody and visitation order. Orders and agreements frequently have notice provisions in them.
What parents "should" do is a different story. There is a difference between giving notice of your travel plans, and seeking permission to travel.
Letting the other parent know where the child will be allows the parent to have a topic of conversation with the child to ask how the beach was or how biking in the mountains was.
There is also the matter of a some accident or other misfortune that can happen. If the other parent is supposed to have visitation following vacation, and the child and vacationing parent have not returned home, it would be nice to know where to start looking.
Factor 7 of Va. Code 20-124.3 includes "the ability of each parent to cooperate in and resolve disputes regarding matters affecting the child."
At some point the circumstances are going to be reversed. One cannot argue he or she must know where the child is going when the other parent travels, and then refuse to tell the other parent where he or she travels.