Would I want to know? No way!! There's no way on earth I would
want to know that my boyfriend slept with my mother!!
That said, I get the spirit of your question, and I do think it's best that JJ tell Paige the truth himself. Right now, she's already mad. She may or may not give him another chance. If she does and finds out later, it will be worse. And secrets always come out later! Not to mention that JJ will be hiding something from her and what that will do to him. Just get it out in the open and take your lumps.
I'm sorry that it will affect Paige's relationship with her mother, but her mother should have thought about that before she slept with JJ... repeatedly. JJ definitely shares the blame, but Eve is the adult here. She should be helping the young ones understand that actions have consequences... not encouraging them to act without thinking about the consequences. I hate it for JJ, and especially for Paige, but - he's already hurt her... she just doesn't know about it. Doesn't change a whole lot. Just get it over with and don't allow anyone else to control you by knowing your secrets.