Yellow Submarine is a great song to start with once they have a bit of coordination with the open chords, and you can start discussing 8th note strumming and counting notes of longer duration, too. I've been teaching that one quite a bit. For the triad stuff, I've been using "In My Life" and this week we are doing "Oh Darling".As I mentioned last time we talked, my kid is in full blown Beatlemania. I finally told him on Sunday he can no longer strum aimlessly in Open G and I've headed down the self-immolating path of teaching a 5 year old how to play power chords on a 1970 Stella acoustic. I'd be interested to see which songs you're using. Feels like it's more appropriate to something like Yellow Submarine than Please Please Me.