My dad fell ill one New years day, he died at the beginning of May. I was 6. I had worked out he was dying but when I asked the adults around me it was denied as "he was going to get better". I didn't believe them based on the fact my mum smashed a plate from her hands when I told her I knew he was going to die. She was washing up, I was drying.
The evening before he died, I was picked up from school by a neighbour who took me to hers and I was there till late (11/12 ish) and was taken home asleep and put into bed. I woke up the next morning late for school, I saw there was stuff from the main bedroom in my room, I went onto the landing and saw my dad laid out for the wake in the main bedroom. I went hysterical.
For a long time, I blamed myself as he didn't get his goodnight kiss. No, it was lung cancer. I had been kept out of the way as he was deteriorating rapidly in the day before.
At his wake, an uncle told me dad was having "a big sleep", guess who had sleeping problems for several years afterwards as I was afraid they would put me in a box and put me in the ground. So avoid phrases like that.
When I was 11, my aunt who lived with us as we were growing up took ill, she had an operation to see the extent of cancer and it was everywhere, stomach, bones, pelvis, lung and blood. She wanted to come home to die, with the help of a rota of neighbours we looked after her and input from nurses and GPs. I sat with her for hours talking to her, (despite the fact she was deaf), I couldn't hold her hand due to pain but she knew I was there. I was there when she died.
Re information, none of it was hidden from me, I was told what was happening and why, I didn't get in-depth info but enough so I knew why some things were happening and that cancer was evil.
Fast forward to 20 years later and the evening I was told by the ward consultant that my mum was not long for this world and to organise any family she would want to see her, I don't have children but my brothers 3 youngest were 7, 4 and 18 months at the time.
He asked me what to tell them, I said give them the "fluffy" version of what is happening, the truth but fluffy,
So the next day they came to see their granny, they hugged and kissed her loads knowing it could be the last time they saw her. We took tons of photos.
They knew she was going to live with grandad in heaven as she was very sick and she would have no pain there. She was very sick but the Drs didn't know exactly why and that was why there were so many machines attached to her.
During her illness, they visited weekly as she held out longer than any of us expected, knowing they might not see her again.
At her funeral, the 8-year-old led us right behind the coffin out of the church. The other 2 released balloons that granny had in her hospital room as sending them back to her.
The oldest of those 2, the 18 month at the time doesnt recall it at all, have said being told the truth helped them come to terms with all easier than it could have been.
It was also easier when a well-meaning family friend spoke to me while I had the 18m and the 4 year old holding my hands on a visit to the shop to take a break off the ward and said, "so is it cancer do you think?" as we didn't know for sure.
She looked down and saw 2 small people looking up at her. The 4-year-old piped up, "no, they don't think its cancer but they aren't sure as granny is so sick and she is going to live with grandad where she wont have any pain" The look on friends face was funny in itself.
So like pp, I would involve your son, give a fluffy version as needed. Only the information that he can handle and bit by bit.
Utilise all other supports possible, make sure he has adults he can turn to and that will support him as far as possible. He can probably see something is going on but isn't aware of how bad it is and not having time to prepare will make it harder.
Have a look thru these -www.thebookpeople.co.uk/webapp/wcs/stores/servlet/article?articleId=top-10-best-books-for-children-about-death-bereavement-and-dying - you will get fuller reviews on Amazon
Also are his teachers / TA etc aware of your diagnosis as they will be able to help support him too.
When you are gone, he needs to keep a routine as normal as possible. That will help and will also be helpful re ASD. Yes, to therapy.
Also when you think the time is coming closer and as you are in hospice now, it is short term. I would look for something he likes possibly a photo blanket with pictures of both of you together over the years. This can be a great comfort. Give it to him and its to comfort him and hug him when you aren't here. Its to surround him in your love and wrap him in your arms. It's also something he can wrap himself in at your funeral if he is able to attend
for you, you are in a horrible position (mentally and physically)