This is such a sad situation for you, Mandymoo. Please look after yourself first. Your grieving will take time, and can't be rushed. Your children will be feeling the same, I'm sure, so you can only hold each other until you start to heal. I wish you better days ahead.
I cannot even imagine what you must be feeling. As others have said you must take care of your own well-being in order to support your other adult children, perhaps if you see it as all of you supporting each other, because you need support too. Am very sorry this happened. 💐💐
My deepest sympathies, the best way to help your other children is to look after yourself first, and then look after them.
There is nothing that can be said or done to mitigate the pain all of you are going through, just grieve as you want to and ignore anyone who tries to tell you what to feel and for how long.