First, as other have written - Ivies are not the best colleges for engineering, except Cornell.
Second,
More than 95% of the unhooked applicants to these colleges are rejected, so even cutting admission chances in half just makes that 97.5%.
Seriously, though, what do you want from a college?
“An Ivy” is just an athletic conferences for a certain subset of private colleges with low acceptance rates. It does not describe anything else about these colleges. They vary a lot in size, majors that are offered, rural versus urban, etc.
Why do you you want to attend “an Ivy”, versus “a Big 10”, or an “Atlantic Coast”?
In my experience, most student who post here “what are my chances for an Ivy?” have not actually thought about attending college, but mostly about being accepted to a college, specifically a college with high “prestige”.
That is not a good way top go about succeeding during and after college. That’s also not a good way to think about your high school career.
High school should be about getting the most out of high school in terms of education, both academic and socially. That includes being well prepared for college. Not “be accepted to the most prestigious college possible”, but “attend the colleges that is best for the student, and being a prepared as possible for that college”. College is about getting the most out of college in terms of education,professional preparation, and yes, social education. It is about the entire four years, not about the few minutes of finding out that you have been accepted to this or that college, nor about the few months that you tell your friends, family,and family friends about the acceptance/s.
So again, ask yourself:
What do I need from a college?
What would I like from a college?
What do I want to do after college?
Which colleges will be the best for these?
And stop focussing on whether two or four Bs will ruin your chances at being accepted to an Ivy.