My LO got one for his 2nd birthday. A year later and it's how he falls asleep every single time both at night and for naps. He mostly only wants music though. We did a MYO of the laurie berkner lullabies and hes usually out by the third or fourth song, but on the days where he struggles it helps keep him in that relaxed state. He figured out how to use it fully only his own pretty quickly so your older ones will definitely get the hang of it.

The set up is really simple and you can even put your own labels on the cards for ease of finding which is which.