i have custody of my childern their father has supervised visitation his mother just past and he wants the kids to attend the funeral

If your kids knew their grandmother at all, they should attend the funeral. But supervised visitation is supervised visitation. I understand your ex doesn't want a stranger (the supervisor) at his mother's funeral. So under the circumstances, unless there is extremely bad blood between you and his whole family, he should not have a problem with you being there. If you can trust his sisters not to leave your kids alone with their dad, they could supervise. But if you have any doubt whatsoever, don't let your kids go to the funeral unless you can attend, too. You don't have to get anywhere near the dad to keep an eye on your kids.