Haydnpat
Dd wants us to move with them
What will you do if the next posting is to Cyprus, Gibraltar or even the Falklands? It could be somewhere in the UK but would you follow them and rent? If you could find a property that is affordable that is.
Yes, my advice would be to stay where you are and visit when you can.
Your son might be unsettled at first but would probably be more so if he is uprooted every couple of years, following his sister and her family around. Will he miss his father?
What does your son-in-law think of the idea too?
Your daughter is an adult with a family of her own now and you will be able to visit them and perhaps you can stay with them to help when the new baby arrives.
Don't rush into anything.