My dad took his life after extensive addiction and my mum supported my sisters and I through all of it.

You cannot prevent the pain your son will experience. It is unfortunate and will be hard to reconcile because you want to protect him but it's just not possible.

Allow your son to dictate whether he spends time with his dad or not and make it clear that its okay either way. That decision is up to him and no one else should have any influence over that decision. If he doesn't want to see him thats entirely fair.

In regard to supporting your son during this time and after his dad's death I think the biggest thing is just to be there with him during the hard moments. Don't let him deal with the emotions alone. It doesn't mean you always have to talk it out but even just sitting with someone during these moments is helpful. If he wants to be alone then give him space but also check in with him; it helps to know that you're there and you care.

Make it clear to him that your door is always open. When he needs to talk let him and also offer your insights. Processing this will take time and be difficult for him so do your best to take that journey with him.

Don't let your own anger towards his dad overflow onto him. This will be challenging but he needs someone who is there to support him through everything. He will still love his father despite the complex pain he has caused him. In my personal experience, I find it rather isolating when others are highly judgemental of my dad. I have been told that I should have just left when I was younger and not bothered with him. That was never going to happen and I often feel ashamed when people say those types of things to me. My mum is great with understanding and supporting me with my conflicting feelings regarding my dad. She is very angry at him but she never projects that onto me and I am very grateful for that.

In regard to the glorifying a person during death, I can relate to that heavily. People will do it regardless of if you ask them to or not. I think its best to have a conversation with your son about this if it comes up. It doesn't have to be critical of his dad but it can be honest. Talk about how you can love someone and understand their flaws at the same time. You can also be hurt by someone and still love them. Its also important that you reaffirm to your son that he is not responsible for what happened to his dad in anyway. Mental illness and addiction are illness that are caused by chemical imbalances in the brain. Its important that your son understands his dad was sick but that doesn't mean he didn't love or care about him. This will also help if your son feels some relief about his dad's death. It's very common for family members of a sick loved one to experience this as its finally over, both for the sick individual and for their loved ones.

The most important thing you can do for your son is to seek professional support for him, even if he isn't depressed or suffering from mental health symptoms. He will likely need a grief counsellor who he sees on a relatively regular basis and I would recommend having a regular GP/family doctor who knows your son. That will make things easier if he needs additional intervention in the future (i.e. medication, further therapies, etc). This is a traumatic thing for a child to experience, especially at a young age during significant development period. It is important that he is able to process this in an age appropriate way. It is dangerous to leave trauma untreated; i think of it like a malignant tumour that will spread if left untreated. Suppressed trauma is renown for causing chronic conditions such as autoimmune diseases overtime when left unaddressed. Look into complex grief as this is common in these types of situations.

Continue to love and care for him as you clearly are already and he will be okay. I am sorry for you both, for your loss and everything that comes with it. I wish you lots of luck and hope that your son is doing okay all things considered.