For some reason my previous comment got killed. Let's try again (with some edits for conciseness, and a mixup of the ages).
1. I think incorporation is too premature. All you guys have is an idea. Its the product that you build that actually matters. While it's a good idea for you guys to come to a basic agreement as to how you guys will divide equity/responsibilities in the future, it is too premature for any contracts to get signed now. For all you know, a year from know the product/idea/team could have imploded; not incorporating means you guys would not have any paperwork to deal with (nor wasted money).
First, build a minimum viable product, then launch it, then see what traction you guys are getting, while iterating. If you guys think you have something, then start a company.
2. I am also very concerned because it sounds like you guys also have school to deal with (you seem to have several more years to go), which will make it very difficult for you guys to commit to making your product a success. Postponing college is an option for the 18 year old (taking a few years off), but if the 18 year old takes a leave of absence from college or otherwise postpones college while you still stay in high school, you guys will run into issues where you're contributing less than the other. I honestly think it will be nearly impossible to juggle school and work while also out-competing people who do not have school to worry about. As you can see, there are a whole host of issues you guys need to think through. Or maybe you've skipped a few grades and I don't know it.
3. A guy you met on the internet (and have never/barely worked with, and have barely interacted with, and have never met face-to-face, and otherwise don't really know personally) is not a potential co-founder. What if it turns out that he's really flaky/lazy/abrasive/rude/generally bad? He is an unknown quantity. It also complicates things quite extensively because you guys have probably never had to manage someone (club leadership does not count). You are better off hiring him as a contractor for now (and in the process gauge his skills and his communication skills and also in the process improve your own project management skills).
If you do go ahead with incorporation:
1. Get parents involved (see if your parents know or are friends with any lawyers who are familiar with incorporation or equity issues).
I am not intimately familiar with how equity is dealt with for minors, but I would wildly guess that a parent of the 14 year old would have to sign all legal documents for that 14 year old and also hold board seats/other contractually significant positions. However, a trust or custodial account might be able to be set up for the 14 year old. I am not sure about this.