I'm sorry, Emmy. I don't have any advice on what to say as my kids are all older. I would agree with the others that you may not be able to keep the children away from your husband for a month. If your mother-in-law is staying with him and you trust her, maybe she could supervise visits with the children? That way, you can minimize your contact with him?
I also absolutely agree with the advice to see a lawyer and consider filing a police report. Like redatlanta says, that may enable you to enforce no contact with the kids now (or at least make a case for supervised visits.)