Last year the big stage was set up on the beach area around Central which avoids the mass crowds going through walking Street.
I am not 100% certain where the fireworks were let off but their were thousands of people on the beach, with plenty of chairs to sit and vendors selling drinks etc. Much safer than previous years. If you head for the Northern end of the beach it's not so crowded.
However, yes it's a big beach which could handle the thousands of people but as we all know the roads cannot. It was absolutely gridlocked with both cars and people on Beach road(pedestrians only), second road and all in between for a couple of hours after, best solution is book a Hotel within a KM of the beach and walk.
It's a good firework display and worth going, just plan a bit ahead and book Hotels early.