You are not obligated to change the terms of the agreement which you and your ex agreed to. Since the agreement specifically states that he is to do the drop off and pick up for weekends, it is his responsibility for the traveling. If there has been a change in circumstances since you signed that agreement such as you moving further away or a change in his schedule which would impact visitation then he would have to file for a modification. However, it just appears that he is tiring of the agreement. This is not your problem and he will have to take whatever steps necessary to resolve it. You could agree to meet him halfway to accomodate him and to maintain contact with your children but I would make sure he reimburses you for travel and it would have to be around your schedule. However you are not obligated to do this and will not be looked upon unkindly if you did not accomodate him.