Hello Titsy,
Ten weeks down the line here, but no young children (thankfully).
It's tough the first few weeks, but I agree with posters above that it's best if he can leave the home asap - you need to be able to have some privacy, and confront the reality (hard as that is).
However, if he starts looking a divorce websites for men - he'll quickly find the advice not to. Try to persuade him now if you can - it's better than you and your children make the adjustment quickly. They will be picking up on the tension one way or another. Agree a contact schedule and then cease communication to all but the banal of arranging the children's needs as quickly as possible.
I read and recommend 'Detach and Survive', not sure how old your husband is but aimed at women whose husbands suddenly want life to be more fulfilled by not being married. So men aged 30+.
Also, I cannot stress this enough: tell your family/friends from the get-go. I didn't tell anyone for two weeks and made my own agony much worse. Having people who will listen, let you cry and just be there for you is the one thing you have over your husband right now. It is likely he won't tell anyone. Don't do things his way - do things your way. Making decisions for yourself (however small) is the only thing you have to give you a sense of control when he has taken the ultimate of decisions.
If later down the road he wants, and you accept a reconciliation, they will forgive him because they love you. If he doesn't you've got yourself invaluable emotional support when you are at your most vulnerable.
Not a single person I have told has been anything less than sympathetic. My feelings of humiliation were all mine, their feelings of compassion has got me to this point. You'll be amazed at the kindness of others.
I know first hand how much it hurts - but I lots of people come out the other side much happier and healthier. Fact is as a woman you are most likely to, your husband may end up better off financially, but not necessarily healthier or happy.
I take some comfort in that!