Consider slipping trail mix into your backpack for lunch. Get the real kind, with dried fruit and nuts. It really is quite healthy, inexpensive, provides more than enough energy to really get you around (trust me), takes up little hassle and space, saves time, and is tasty, too. Though I've never been to Oshkosh, I've been to other walk-a-million-miles-in-the-sun type events, and let me tell you, you won't know the difference between trail mix and a really nice lunch when there's so much to look at! (In fact, I have often forgotten to eat altogether!) Sometimes I also bring m&ms (if it's not too hot). I've never regretted doing this. But water! Oh, please don't forget water!