The linux version of U-he Hive may be the quintessential EDM choice,
in the $150 range, but some 3000 presets are available,
between the factory set, and those donated freely by Hive users.
Free/affordable instruments include U-he TyrellN6 and Podolski,
with magazineware Beatzille/BazilleCM, (lite versions of Bazille)
There are 20 how-2 videos for BazilleCM with the CM digital magazine
which is $5 from zinio.com, downloads of the dvd content are from filesilo.com,
(CM digital 'magazine ownership' is verified by finding a word from a header
in a magazine article, viewed from zinio's reader app.) This months cover dvd #257
features a great version of the Thorn synth, probably a good EDM choice)
Also, the powerhouse Fathom synth has a free mono release, and the full version
is due for a $12 sale real real soon. These work in reaper/wine,
might work via linvst/airwave wrappers, and the linux synths work in
most linux hosts.
Linux RaveGenerator2, and discoDSP's linux OB-xd version, are also free,
and with effects from rakarrack, and Guitarix, can also enhance the genre.
Matt Tytels' Helm is a free cross-platform powerhouse, a popular synth contest
entry songs are here: https://sites.google.com/site/kvrosc/osc-90-helm
There is a powerhouse synth called Wiggle, that I'm sure your son would love,
and it's many features all seem to work fine in Reaper/wine. Wiggle has
unrestricted 20 minute demo sessions to test/learn with, and I believe the 500+ sounds
are in the EDM range. It's only $50 at the moment, at pluginboutique.com
Summer rocks for the chilllldrennnnn!
Of any age...