what do you do if you are an international student applying to a few ivy league schools

Answered

First thing I'm going to say is that, international or not, there is absolutely nothing anyone can do to "make sure they get into at least two" Ivies. It is incredibly difficult to get into even one of those schools, and getting into two or more requires not only an extremely strong profile and stellar essays, but a lot of luck as well. The best advice I can give is to not bank your future on getting into one of those schools — have a back-up plan for yourself. As for extracurriculars and the like, these schools will judge you based on the norms for your school and country, so you should aim to pursue interests or hobbies on your own (e.g. learn a programming language, write a novel, something like that), or take whatever avenues other students who've applied to these schools have taken.

In truth though, the thing that complicates the process most for international students (vs. US students) is financial aid and ability to pay. All schools besides HYP, MIT, and Amherst are need-aware for international students (unless you're from Canada or Mexico, but it doesn't sound like that from your post), which means that they take your ability to pay full price into account when making an admissions decision, and have very limited spots for international students who apply for financial aid. If you are able to pay full price, getting into multiple Ivies might be possible. If you aren't, your best shot is to aim for HYP, which is obviously the most competitive group of these schools, and try your best to get into one of them.