Reintroducing father and 3yo

My sons father and I split up over a domestic dispute when my son was 6 months old and there’s an order preventing us, or him and his son, from talking until November. I just ran into his side of the family at the fair yesterday and it sounds like he’ll want to meet him again when this order is up which I’m okay with as long as I supervise. Do you have any advice on what I should be doing to prepare for the meet since it seems likely that it will happen and how to reintroduce him comfortably?

Also, he has a fiancée and advice on introducing her would be great too