welcome joslyn-
at this stage, it would be good to switch the focus from him and onto yourself and your children.
i don't think it's a good idea to have him speak to his son. you are the sober, sane parent here.
in making your plans, i found it best not to rely on my alcoholic to do anything. i made my plans 100% independent of any action of his.
of course, you could ask him to leave the family home until/if he gets his act together. he might not go tho.
please, protect yourself financially. full blown relapse often is accompanied by financial ruin. for example, have your paycheck deposited into an account in your name only and get off of any combined car insurance.
you're in the right place here at SR. keep posting. there is a lot of experience here.
naive