When my nieces/nephews come to visit they like The Beatles the most. I don't think they're even fans of the band but they just love that pin for some reason. I think it's all the bright colors and spinning record disc that attracts them to it. Willy Wonka is probably their second favorite and Mando would be third.
They don't really care for the other kid-friendly stuff like TMNT, Avengers IQ, or Jurassic Park home pin.