Would you notify the principal about your ex (father of kids) being a RSO?

I am looking for advice fellow parents. I'm in an unusual situation. My ex, who is father of my tween kids is a Registered Sex Offender. I just found out today that he has emailed the kids principal. I don't know the context of the email, other than that he was letting the principal know he was sending in a check for payment for a field trip. I haven't mentioned it to the school prior because he was in jail, and I just didn't want to deal with the stigma that comes with it. He is as far as I know a level 1, which means he isn't listed on the sex offender list/website. In the past month or two, he has mentioned that his PO has said he could attend school functions. I haven't given him any info on any functions, as I don't agree that he should be allowed. I don't have contact with his PO, and if I were to call and ask questions and voice my concern, my ex will make life difficult for me. I feel like I should 'warn' the principal of my ex's status, but since he and I aren't getting along, I want to make sure that my instincts to notify the principal are reasonable, and not troublesome.. via /r/Parenting http://ift.tt/2qylc1G