I was planning to read a lot of source code, write a lot of code/contribute to open source, and study formal CS on my own. I think after 3-4 years I would have as much programming and formal knowledge as if I had stayed in college, and maybe more. I want to do this and would find it fun.
I'm wondering if the lack of a degree would hold me back significantly. That seems to be my parent's main worry.
Having a degree from an Ivy school will help you as compared to an ordinary degree. I went to a middle of the road state school and I have seen first hand that many "people who matter" are materially predisposed towards favoring those with degrees from fancy schools. Some could argue it's rational. I'm talking about employers, investors, and even in regards to dating.
If you leave school you are likely to find work without too much trouble, but you'll be somewhat worse off than a guy with a degree from a middle of the road school. Outside of silicon valley a college dropout may face a greater headwind than inside silicon valley.
If you can become the next Mark Zuckerberg or Bill Gates, it won't count against you at all. Notice that they both left school for a very good specific opportunity.
The best thing about graduating from a great school is the relationships you'll build with other smart guys. I'm not sure why, but most lifelong friendships seem to be formed in school. Learning alongside those smart guys is also highly motivating.
Finally - if you leave school to get away from your parents pressure, you're letting their actions control your life. You are an adult now. Take charge. Don't let rebelliousness push you around. Choose carefully, realizing that a degree from a top school is a good opportunity.
I'm wondering if the lack of a degree would hold me back significantly. That seems to be my parent's main worry.