You haven't even been served. Depending on your jurisdiction, you will be given 20 or more days to file an answer. Even then, in the early stages of a lawsuit, it is customary to get a time extension.
If he wants to move that quickly, and he is causing so much drama, why not ask him to go somewhere else until his apartment becomes available (presumably why he wants to move on the 30th?).
Why not suggest you guys tell the kids now. Then he doesn't have that as a threat over your head and he has to begin dealing with the consequences of his action, something these folks don't like.
When I did extensive research on the topic, most things I read said tell the kids a while before the move out to give them time to adjust. He's down in the basement anyway.
Maybe telling the kids and suggesting he go ahead and move will be enough to target his energy in a different direction. It will at least show him that you are not trying to hold on and are taking steps to get him out.
He's just going to continue to badger you otherwise.
