I say go with Pepper, with the addition that the kids get to find out their legacy once they grow up. Pepper sounds like she’d understand keeping the truth from the outside world and help Conrad if he decided to trust her. As for the kids, maybe they noticed how many secrets their parents were keeping, and they find the truth. Maybe the twins go to help their step-brother find out what happened to his father, and their powers change or grow stronger. Magi may even decide she wants a chance to know her kids, that the risk is worth it. Then the kids get to decide if they want to plunge the magical community into chaos and war, united as brothers or as rivals for power. Would they want to team up with their mother and rule together, or get revenge for their childhood in exile? Each of these kids has the makings of a Chosen One, whatever that would look like.
Conrad deserves a happy ending, but the story is too good to end in quiet oblivion.