The park will fit the people but maybe not in the same concentration as the stadium you are picturing. Will that stage fit in the park? maybe, its a big park..
Not sure if you are more interested in the venue or the event
The fete National is one big party that is played out all around the park even if you cant see the stage, a concert in a stadium is more of a show where people come and watch a particular band for a few hours then leave whereas the Fete National goes on most of a day and well into the night and sometimes the whole weekend..