If you don't have the information your ex needs, you can contact your COBRA health plan administrator directly to request the information again. They will be able to provide it to you.
If you cannot afford COBRA, there may be other health insurance options that will provide the health coverage benefits that you need for you and your family. If you and your kids are healthy, you can get health insurance much cheaper than COBRA here:
http://www.cobrahealth.com/healthquotes.htmEnter your zip code, then click the button. It's important not to apply to just one carrier, you should find out what they all charge, and it does not cost you anything but some additional time.