I can't quite figure out the 2nd sentence.

[Satyr]

El evento arrancó con cierta demora, debido a que sobre la hora de comienzo seguía llegando una gran cantidad de público al club.
The event started late because lots of people were still arriving to the club during the first hour.

La presentación estuvo a cargo de las patinadoras mates, que interpretaron una coreografía denominada “Árabe Night”.
The introduction (or presentation?) was in charge of the skaters mates that performed a choreography called "Arabian Night".

[Rusty]

My guess is skater pairs.
Where did this sentence come from?

Instead of during the first hour in the first sentence, it should probably be around starting time.

[Satyr]

http://www.diariobuenosaires.com.ar/...DNoticia=25891

[Rusty]

Thanks for the article. It looks like it's a place name. The skaters were from El Mate. They were in charge of the event.

It is common to give a people from a certain area a nickname. Those that live in El Mate are known as mates. Those that live in Costa Rica are called ticos. Puertorriqueños like being called boricuas. And so on.

[CrOtALiTo]

Yes, Rusty, you are right.

The article speak above a place nor a name or nickname.

Then the skaters were in the Mate giving a show.

[sosia]

Agree with Rusty
"Fiesta de Patín en el Mate " --> patinadoras mates
It's like
"The Lakers begin the Conference" --> the angeles cheerleaders

Saludos