Here is some honest advice, I would suggest reading it.
FPSC is really not that bad I don't see a problem with you getting it
BUT it's ultimately your parents decision. I would go to the website and tell them to download the free version and see for themselves if it is really that awful. If that doesn't work then fake a British accent and pretend to be from the UK (it is only rated 12+ in the UK), LOL. If they don't let you get it, accept their decision, wait a year or two and when most people have capable computers, purchase x10 and make some games. Good luck.