Taking child overseas with out biodads consent

Ok my child is almost 9 bio dad hasn’t been around since my child was 6 months, I have since got married and had another child to my husband. my mother in law wants to take us all on a holiday overseas as a family but I don’t know how this can happen?
Can anyone please shed some light on the situation?

(Ex was very violent and have had many intervention orders against him.
I don’t know where he is nor do I want to, he is constantly in and out of prison and I do not want our life tipped upside down by having to make any sort of contact.
I have very bad anxiety right now even just thinking about this is going to set a major attack 😢)