Honestly, I would just go ahead and talk about it with him. I mean it's not immediate then it's likely he will just help you uncover the reasons for your suicidal thoughts. As the date gets closer he may ask you to come in more frequently to ensure your safety. As far as what good it can do sometime just letting out that those thoughts are there helps release their grip on you. For me, talking about the suicidal thoughts releases the "pressure" to act them and given it sounds like there's some time between now and when you plan to act, it also might serve as a way to resolving the things that leave you feeling hopeless and like life is pointless.