Personally I'd keep the clubs and the holiday and the charade going until February. But that would be the time that I'd leave knowing he was gone for a few days.
He'd come home to an empty house and divorce papers. You are not currently in any hurry.
Ok so if you've got access to a fair amount of money say a couple of thousand get recommendations from discrete divorced friends, collègues, acquaintances or whoever for who is a good divorce lawyer. There are some big London names but they come with big prices tags. (Do this today because once word gets out that you know the game will change.)
Then get appointments with them all. This is helpful in 2 ways. If they've seen you they can't see him. And finding a lawyer that "fits" is harder than you might think. Mine was my 4th and has had my back for 9 years of court cases with my litigious ex.
In the meantime:
start looking for and copying all the paperwork you can find.
Open a new bank account online away from your usual bank and put in as much money as you can that won't be missed. Move any child benefit payments etc to it. You can also transfer half the contents of joint accounts but that will give the game away so the timing needs to be carefully done.
Make sure you have a clean email address that he does not know about or have access to via other devices. Change every password.
Assuming you've a smartphone download Evernote and an app like Scannable which will scan documents using your phone straight into Evernote. Evernote is accessible from everywhere and syncs automatically. (You might need to upgrade it but I think it's good value for money.)
Mortgages
Bank statements (back as far as the business sale if possible)
Passports
Investments
Car, bike, boat, racehorse etc purchases
Pension statements
And anything else you can think of.
Any receipts for dodgy purchases - so not for you or kids
Then write a time line of what you know.
So married in x
House bought in x
DC1 in x
D.C. Problems diagnosed in x
Sold business in x
Bought stupid toy in x
This helps the lawyers and is useful for you in working it all out.