It's a bit hard to follow, but from your description, it sounds like you were close hauled on port tack (with boom to starboard), and then decided to reverse course by bearing away to a broad reach or run? If so, you did well to ease the mainsail out during the turn. But you didn't mention easing the genoa. If you neglected to ease the genoa, it's possible that it was the source of your knockdown. If it remained sheeted flat for close-hauled sailing, it would present a lot of surface area to the now-perpendicular wind.
Remember that whenever you make a course change under sail, you must do one of two things: Either you must change the trim of all
the sails, or you must alter the direction that the wind is coming from such that the apparent wind remains constant. Since so few of us have command over the wind and seas, we are left with little choice but to change the trim of our sails.
It sounds to me like you're getting the hang of this concept pretty quickly. I'll bet that was a fun ride for your 13-year old!