Hello Xertaboy

The discotecta in Roquettes would probably be best  - they have 2 rooms - one that plays house music for a younger crowd and a smaller room that plays Catalan Dance music. The entrance is opposite the cinema (however get your son to check which night is on as sometimes it is gay or under 18)

In the same building but with the entrance to the main road is another small Club that plays rockish music

By the old bridge (Roquette side) is the Aussie bar which is usually full and plays a good mix of Catalan Dance / House Music

There are various other smaller music bars and clubs in the town