If other people know you are splitting up, you really should tell your children. There is no excuse not to and your husband not wanting to tell them is just manipulation on his part. I'd let him know I was going to sit them down and tell them at a certain time (soon) and if he wants to be there, fine. If not, you'll do it alone, but they need to know what is going on. They KNOW something is going on and it's possible what they fear is happening is much worse than what actually is, so it's only fair that they know.