My kids are still a little hesitant to grab the sticks and play, but really love holding controllers while watching me play. My daughter is an EXTREME perfectionist and gets angry if she can't do something on the first try. I'm working with her and hope to get her playing some SMB again soon. Kudos to you and your kids!
LOL, I could say the same for my wife! When we were heavily into the original PlayStation, she'd get stuck on some deal in a Spyro game and just hand me the controller to take care of it for her. Nevermind that I hadn't played 50% of the game up to that point, I was just "better" at games than she was, so she assumed I could figure it out and pass that spot for her. After about 12 tries, I usually did.
Congrats on getting your kids interested in a classic. I did that with some of my previous foster kids, got them started on SMB, Contra, etc. Unfortunately, the boy we've had most recently wants nothing to do with retro stuff because it's too hard. All he wants to play is Mario Kart 8