Just chiming in with my support since I noted you said you were amazed how many in this sit. Husband moved out 11/30, Saturday of Thanksgiving weekend. We told kids (8 and 11) the day before the move out, because husband did not inform me his plans were definite until day before Thanksgiving: That's right, 3 days before (although he had told me he was planning to move out 6 weeks prior, I thought I was DB and it was going well).
As for the talk, although it was move out, not D, I let him do the talking, since how could I possibly explain? I just did a lot of hugging. All day. Occasionally will still say something to 11 year old when he is having trouble, like I have done everything I can and am still trying, but I can't control...
M 20 yrs me 47 H 51 s11 d8
BD 10/8/13 H Moved out 11/30/13 OW slept over with children Dec '13 OW moved in w/H Jan '14