I agree with seesaw and if you are taking on a leadership role then you don't want to put this CEO's son on the defensive. Perhaps when it comes to situations like this it's better to look at these requests as questions instead. For example, instead of hearing it as "just say you have been handling this account all along", you can think of it as "can we just say you have been handling it all along? ". This can give you a chance to enlighten this CEO's son with a better approach that can become more productive, especially if the client isn't all that happy with how the account has been handled. You could say to this client that bought out the company "Hi I am Have Hope and I see you are the new owner, I have just taken over your account and am looking forward to us both working together in fresh and positive light".