I think you have a really great perspective about all of this! It’s important to know what would make you happy, and it sounds like that is not an Ivy League school for your undergraduate education. You’re not the only one–that’s exactly how I felt when I was applying 14 years ago. I knew myself, and I knew I wouldn’t be happy in that kind of environment.
Now it sounds like you’ll probably have to apply to a few Ivies to make your parents happy–do it to see what happens, because they may be shocked to find what you already know, which is that many fantastically qualified students are rejected from Ivies. Or you’ll get in, and go from there.
I would have an honest conversation with your parents, and it will benefit your sister, too, to have it. Talk about applying to a range of schools–reach, match, safety–and explain that you, too, care about your education and you’d like to approach all three tiers with strategy. Especially if you are a great student, your match schools will still carry prestige. And then for safeties, perhaps a good strategy (especially if money isn’t an issue for your parents) would be honors programs at state universities. Or, if money is an issue, your safeties would be schools like Alabama for their automatic scholarships, and privates that are generous with merit aid.
Ask how many schools your parents will pay for you to apply to–some parents, frustratingly, will not “allow” their child to apply to schools of which they don’t approve which can cause issues, but hopefully they are willing to support your applying to a generous range, including less prestigious schools.
It may actually help if your parents were to come on CC–do you think they’d be up for that? One dip into the Parents forum might set them straight, re: Ivies or bust…
Good luck!