For a large vehicle that could hold 3 people and lots of luggage try the limo service
http://www.silverstarcar.com/Owner is an American expat with a Lincoln TownCar. A little more expensive (US$88).
Also you can exit secure area, go to locutorio in terminal, and call one of the big cab cos and ask for a
taxi familiar or
camionetta to meet you in front of the McDonalds right outside the locutorio. These are small SUVs and can hold 3 pax and lots of bags. The cab should not take more than a few minutes to arrive to the terminal as many cabbies wait just outside the airport for these orders after dropping off an airport pax. Taxi del Plata 4504-7776, 4505-1111, Radio Taxi
Pidalo 4932-2222, 4956-1200, Radio Taxi Premium 5238-0000, 4374-6666. Fare with tolls should be no more than 90 pesos.
Or you can use my friend, Elio , a cabbie with a camionetta. He would wait outside the secure area with a sign. Assuming you arrive more or less on time so that he isnt there waiting endlessly, he will take you downtown etc for about 120 pesos. He doesnt speak English but that is not n insurmountable obstacle.