How to raise children

I'm agnostic. Grew up Christian attending a cult like church. My children were not raised religious but my now ex husband is pushing church and Christian beliefs down their throat. I feel angry about this since I have sole legal custody and get to make the decisions. I think my biggest frustration is he is a sec offender sends me text messages to find god and "god bless you" "go to church" I just don't know how to deal with this when my kids start asking me about things