Guys, remember, it's a celebrity party, not a business party. And he's a DJ. It's doubtful he'll be being served at a table or something similar. We don't even know if a meal is being served. It's likely that some snacks and drinks(not even going to try to spell the right name for it) will be served, but it's also doubtful that we'd be able to poison his food or drink without being noticed while it's in his hand, and it'd be difficult to make sure he got the right one if we poisoned it before-hand. Sniper positions are unlikely to be found, and silenced or not, the glass we shoot through will reveal our position pretty well, I'd say.
Ceramic knife concealed in boot, valet clothes, silenced revolver(no shells lying around), syringe with high dose of potassium(potassium levels skyrocket after death anyway), small amount of heroin(to make it look like in overdose if necessary), 3 fake IDs, fake job contract, and there are three getaway cars and two motorcycles ready with four different routes to get us out of the city afterwards, as quickly as possible. Garrote wire with wooden handles that can be connected and stretched to look like a coat hanger.
Always have multiple plans and tools ready. Keep the MO varied.