How do you think Ollie would react to knowing Dinah slept with Ray?
Dinah learned of Ollie cheating with Joanna Pierce. But, as far as I know, Ollie never knew of Dinah sleeping with her eighteen year old protege The Ray (when Ollie was dead, btw). She was... in her thirties, I want to say? Dinah's age is very hard to tell. She was at the very youngest in her late twenties and in a mentor role to Ray.
As far as we can tell, DC has thankfully retconned this to hell and back. The last time Ray and Dinah interacted in one of the Pride issues, there was no sign that that ever happened.
I've seen some fans say Ollie would dump Dinah if he knew. Even if Ray was over the Age of Consent, it's sketchy behavior. Ollie gave Hawkman a berating for dating a teen ten years his junior.
I don't know if I'd go that far, but it'd be some interesting drama. Ollie is particularly protective of children and young adults.
I don't think Roy ever told Oliver about that one time Dinah accused Ollie of grooming and statutory raping Mia. I'm pretty sure Ollie would dump her for that.