I've been wanting to think on this too for our trip. So I will brainstorm some here...
I'm not sure if you will be in the mood for soup but here is a super simple recipe that just involves canned goods. If you double it, you will have some for a few days. Add spices though or it is too bland, otherwise it is good. Especially if you add some sour cream and tortilla chips.
http://allrecipes.com/recipe/six-ca...etail.aspx?src=ShareOnFacebook&recipeID=19766
Here is a Real Simple Ravioli Lasagna recipe that literally takes me 5 min to prepare since I have done it before. It then cooks in the oven for about 30 min. It is good and quick.
http://www.realsimple.com/food-reci...last-minute-lasagna-10000000610496/index.html
Fresh fruit and fresh veggies if you don't mind them raw, along with some ranch dressing, are very low prep.
What about microwaving baked potatoes, served with various toppings (cheese, sour cream, bacon bits) and a bag salad.
For Lent one year, we were trying to simplify our meals and were eating meals from poorer countries around the world. When we were doing Guatemala, we discovered one of our now favorite quick meals. We get refried black beans in a can, heat them up (add spices if you wish), and then fry some eggs and tortillas and put them together. Tortilla, spread beans on top, add egg or two, and fold over. Add salsa and sour cream if you like.
Frozen pizzas for when you really don't feel like doing a thing but turning on the oven!
You could also google 4 ingredient meals and I bet those would have lower prep time then most recipes (though I am not sure how tasty they would be-- would definitely add spices to some that I have seen for some flavor)
Are you driving or flying?
If you are driving you can bring along your crockpot if you plan to go back to your hotel during the day. Throwing meat and veggies in doesn't sound too bad. Also...some people do crockpot freezer cooking. They basically prepare a bag of stuff to go into the crockpot and then freeze it and pull it out when they need it. That might be helpful to do ahead of time and take down in a cooler and use when you need it.
If I were you, I would try to make several big meals and have leftovers that can be heated so you aren't having to cook every day/night when you get home exhausted from a day at the park.