So that you DON'T look like the mad ex wife in court....start documenting everything NOW....
Write down each time either kid has gone to stay with him only to discover he went out and left them there alone.
Dates - times - if you know for a Fact that he was with any other woman, mention that also....Everything.
Ask a counselor or atty. about documentation.
Your own counts !!
Your 11 yr. old daughter needs to understand it is not safe for her to stay with him....he is UNreliable.