Road trip with me and my friends?

My two friends and I want to go on a road trip when we are eighteen we'll go the summer after senior year. Just some questions, we plan to go to the Grand Canyon, maybe Disney Land. We were planning on going for two weeks, but we don't want to spend a lot. What would be some ways to conserve money, and how much should we bring? Also, the most important is that one of my friends has really strict parents that usually say no. Just wondering how to get them to agree with a road trip and show them that we are responsible? Thanks.