I don't want to make you feel worse than you already do, but I really don't think this will work in the way that you want. Sorry. 
Some separating couples manage to live together while maintaining separate lives, but they are very much notable for being a tiny minority, and in all cases it is because separation is wanted mutually and with no hard feelings.
Your H is in denial. It is highly likely that once he considers your separation to be a real event that he can no longer pretend is not happening, his 'amicable' demeanour (which at the moment simply means non hostile) will change. At best he is likely to be sad, wandering round with an aura of kicked puppy about him, which will make you feel terribly guilty and your children terrified of upsetting him further. At worst, he may become horribly belligerent or even downright nasty.
Living separately may not be an option for you because of finances or whatever, but I would urge you in strong terms to tell your DC what is going on. While it comes from the best of intentions, you really cannot hide this from you. They will suss something is going on (and what they come up with in their imagination may be worse than your separation). That could be more damaging than knowing what is going to happen.
Far better to face this as a family so that everyone can adjust at the right pace IMO.
Good luck.