Well done in getting him out, but have you told anyone in your families or friends yet ?
This doesn't matter right now, but when the corona crisis passes, your DC will hear things from other sources.
I still think you MUST tell everyone what your H is doing/ has done and that the marriage is over so that you and your DC get the support you need and deserve.
As for what to tell your DC, I'd tell them small snippets only and on a par with their level of understanding.
Eg, DC - ''Why is Daddy not coming home tonight ?'' YOU - ''Mummy and Daddy don't want to live together anymore because we kept having rows. Daddy is going to live somewhere else so we don't row any more.''
Just keep it simple, and don't say you don't love each other anymore, just say that neither you or your DH want to keep fighting/ arguing etc because then no-one is happy, and you both want a happier life.
The kids will pick up from other sources what he's done, and come to their own conclusions in time.
Be prepared for your H to tell them nasty things such as ''I want to come home, but your Mummy won't let me''. Just answer these truthfully and simply eg. ''Mummy and Daddy can't always agree on things, just like you and your brother/ sister don't always agree.............but we both love you just the same and that will never change''
The DC will usually blame YOU for a while, but it will change to blaming your H later.
There will probably also be a time in the future when you may need to actually defend your H when the DC realise that it was HIS affair that broke up the family.
It's important that YOU never say it's his fault, just try some escape phrases like '' I know you're angry at your Dad, but he's still your Dad and he loves you. He's maybe just not as good at being a Dad/ husband as others..................just like you may be not as good at making friends/ playing football as someone else................it doesn't mean that you're a bad person just because you're not great at something''
As they grow and their understanding matures, YOU will be the constant loving parent who has never said a bad word about their Dad. What they think of HIM will be in his own hands.
I wish strength and happiness for you and you DC, because you all deserve it x