It's so hard to reconcile the idea that someone could do this to their partner when you couldn't fathom doing it yourself.
Forgiveness is something that is very unique to every person and each situation. Don't worry about whether you're "supposed" to or not. This is your heart, your journey.
I'm so sorry for the recent discovery - each new revelation is like a fresh knifewound. Keep putting one foot in front of the other, and remember that you don't have to have any answers right now. Right now it's about breathing and taking care of yourself and your precious children.
When you feel like you have time to process, please share how you found out about the EA's. There might be an indicator in there as to how this is going to shake out.
Just take things in small doses. We're here for you.