Can I get something in writing saying for him not to have my kids around her
Unlikely if the only reason is you don't want her around.
See a lawyer and then you'd need a court order to enforce it.
Probably only if you have very serious concerns for your children's welfare. And you'd need to be able to prove it in court and be prepared for a long court battle. Just not liking her or him cheating on you with her won't be enough.
She pepper sprayed him 3wks ago cause he was at. Another females house and the other females child was injured when she sprayed him in the girls house so now she has 9 pending charges including in danger of welfare of a child I don't want my kids around her
You need to talk to a lawyer Shi. You may be able to do something with the pending charges - at least temporarily.
Only if she is a danger to your children.
Go to the police. You may be able to get an intervention order against her so she can't go near your child and he can't take her there. Get legal advice. If you can't afford a lawyer get advice from a child protection type of organisation/ charity. Or speak to a domestic violence service as they should be able to advise you. It all depends what country you live in. How you do these things varys from country to country. In the short term you can try not letting him have your kids but he does have rights so you need to get protection measures in place for your kids. Make sure everything is documented. Police reports. Reports to domestic violence services. Any past incidents. does she have priors? Does he? Every incident. It will help if it goes to court. I can only imagine how scared you are. You are doing the right thing by your kids. Speak to your local domestic violence service. If they can't help you directly they will be able to tell you who can. All the best.