Is your ex only doing that so you can't go out & have fun why the kids are away...I believe the old saying they don't want us but don't want no one else to have us either...Tell him to let them have his car to come back & forth & see how quick he is willing to do it...One time drop them off & call & get him to let them come home in his, I promise it won't happen...Don't give in their old enough to drive then remind them this is their dads doings NOT yours & don't let them push your buttons or it will only get worse...Stand your grounds or you will pay for it the rest of your life...Remember men just like to push us around & don't care if he uses the kids to do it either...

Promise tell your kid to go live with OW & your ex & I promise they won't stay long...Plus your ex probably stop pushing your buttons because he won't want them interferring with his love nest...He will then watch his steps...Let him know they can live with him & come see you when they want & let him deal with the everyday problems & not just have all the fun & send them home to you when he wants his privacy...