While this isnt the answer you probably want to hear I suggest you listen to your parents. Don't be offended but you are only 15 and while things most likely would turn out to be completely fine, if things turn for the worst it's not worth the risk. I recommend as much as it may change the atmosphere of your adventure convince a parent or older sibling to share the trip. As I've found growing up, Arguing just makes things worse, put your maturity to its test and just have a good old chat with your parents.
Good luck!