The games your kids are playing have been doing a surprisingly good job of exposing them to orchestral music. The Video Games Live group tours and plays the tunes live. Their latest compilation isn't their best, but does have a few notable songs.
Bach: Harpsichord Concertos - Andreas Staier - Freiburger Barockorchester - Harmonia Mundi 2015
Yo-Yo Ma | Arc Of Life
Maurice Ravel: Piano Concertos – Yuja Wang, Tonhalle-Orchester Zürich, Lionel Bringuier (Audio video) • http://facesofclassicalmusic.blogspot.gr/2016/09/maurice-ravel-piano-concertos-yuja-wang.html
Yundi Li - Chopin: Preludes
A beautifully performed collection of some exceedingly beautiful music.