There is a statute that must be followed (452.377). You are going to best off having an attorney help you with this.
The contents of this post do not establish an attorney-client relationship. Any comments made in this post are general in nature and may not apply to the specific facts and law of your case.
This is what family law courts are for. In the court in which the current custody order was entered, petition for modification that includes the rights to move the residence of the children. Be aware that movaway disputes are difficult for family court judges, who must weigh a variety of factors. Perhaps the most important concern will be how the move impacts on the ability of the children's father to continue his present involvement with the children. You, of course, can live wherever you wish. What the court maintains jurisdiction over is where the children live.
Best wishes for an outcome you can accept, and please remember to designate a best answer.
This answer is offered as a public service for general information only and may not be relied upon as legal advice.