Oh my dear Kentish, such sad news. We know it wasn't unexpected, and we can be glad he is not suffering, but that doesn't stop our hearts breaking, does it. And we know that we have grieved a lot already, but that doesn't stop the tears falling.
You may well feel numb for a while, too. And lost. And we will all say 'look after yourself', which indeed you must try to do. But really, just take it easy, hold those beautiful children close and let yourself remember all the good times. Know too that you did absolutely everything you could to make these last months and years for N as good as they possibly could be. You were his champion, and an outstanding one at that.
Sending love, hugs and understanding. I'm here if you ever need a listening ear.