If he wants this, you need to make it "fair"
He needs to wait until you are fully healed and recovered, baby at least 1 year old.
Even ups. Each of you should get the same number of "free" nights, and you each do whatever you want.
NO vetoes. Otherwise, he's going to veto all of yours. If you want to fuck 10 guys, you should be allowed to.
If he is stupid enough to say "yes", fine. Get both of you on Tinder and say that you are looking for FWBs. With a week's notice, he'll be lucky to get one, but you should easily have your pick of a dozen guys.
It's an unbelievably stupid man who thinks he can get anywhere near the sex that a woman can.