There is a cafe/restaurant upstairs at EZE landside. (That said, if you have a baggage cart in tow, think about how you are going to get your luggage cart upstairs.)

There are also some seats generally available near the upstairs departure tax collection window. (But keep in mind how you are going to get your luggage upstairs.)

With a lot of luggage waiting for 6 hours either on the ground level or upstairs, one word of caution: not necessarily easy to use the bathrooms.