Chazal say that if one eats on the street ["בשוק"] he is similar to a dog and is disqualified as a witness. Not dignified!! What is the din of a picnic? A person takes his family to Central Park, lays down a blanket, takes out some sandwiches [prepared by his devoted wife because it is well known how many men have trouble making sandwiches...], some fresh OJ not from concentrate that Rebbetzin "Ana" [as in אנא" ה' הושיעה נא"] prepared herself on her "tropic"al island and cookies and the family feasts - as they fly kites, play catch, take pictures of birds etc. etc. Sounds like FUN!! But is it considered "אוכל בשוק"?
One could argue [I don't like arguing...] that since the family sits in one place it is "mechubedik" and thus not categorized as אוכל בשוק.
"Food" for thought!!!