I feel like he just need to spend energy to get through that. Some people would only stay at home eating chocolate, some others need to keep doing things...
Getting drunk and going out partying seems like a reasonable way to cope with grief, it's been said countless times already but everyone grieves differently.
Come one 2-3am is when people start getting into the club/disco in Spain, I don't see the problem, he probably need to have fun and don't think in his mother right now