I’m sorry to hear about your Mum 💐, this is the last thing you need right now x
Only you know what’s best for your DS, but hopefully different opinions will help you to decide.
Obviously, this is all only my opinion.
Firstly I would pay privately for DS to be assessed. I would have to know whether he’d been subjected to anything himself, including ‘innocent’ photographs. I’d get this done ASAP & before talking to DS about his father.
I would be asking the police what they do to see if he has photos of DS.
Then I’d talk to DS. I think 10 year olds can handle the truth better than being fobbed off. I think you risk really damaging your relationship with DS if you’re not honest with him.
He’s 10, even if he doesn’t, most of his mates will have access to the internet. The last thing I’d want is him finding out via google.
I would explain that the police have found out that his father has been doing something illegal and hurtful to children. Then I’d explain what he’s done, in very broad terms.
I would tell him that he won’t be able to see his father, that he will be in prison (one hopes anyway) for a long time. If he asks about calling/Skyping then I’d explain it can’t happen right now, but maybe at some time in the future.
Then talk to him about his siblings and their Mum. Explain that she’s trying to excuse what he has done and there are no excuses. NONE. Tell him that you won’t be seeing them for a while until she understands that what their father did isn’t excusable.
It’s hard to accept that someone you love could do something so awful, there’s a real disconnect. He’ll go through a lot of different emotions. I’d tell him that he can talk to you anytime or you’ll find someone neutral he can talk to. Tell him it’s categorically not a secret, but it might be good not to tell his friends etc for a while, because you can’t untell stuff and later on he might wish he hadn’t told them.
It’s bloody tough on you both.
Poor DS x
...and all of the children involved.