Monthly visits are never fair and honest. (Every other weekend is unfair, for that matter.) Figure out how to make the car ride enjoyable (books, games, songs, DVD's, I Spy, whatever). They need to have a healthy relationship with BOTH parents and you need to take responsibility for making their relationship with their father a positive one for their sake. And that includes making the travel time to and from positive. Quit using your children as pawns to punish your ex. Are you saying the drive CAUSED your kids to get sick? Either that's baloney or someone has an unhealthy car and maybe it needs to get checked for mold or carbon monoxide.