All a 33 on your ACT's does is not get your application rejected immediately.
Also here's a quote from a NY Times Article on Harvard's admissions statistics which is mirrored in other Ivy's to an extent:
"Harvard admitted 2,032 students this year, or 5.9 percent of its 34,302 applicants, officials said. (Last year, Harvard admitted 6.17 percent of its 34,950 applicants.) This year’s applicant pool included 3,800 students who were ranked first in their high school classes."
3,800 kids were valedictorians who applied. Only ~2,000 are let in. Chew on that.
Harvard's track team is no joke. I'm not saying those times are bad by any means but with the strength of their team unless your coach knows the Harvard coach or something like that it's not much of a help.
Personal anecdote; I'm currently a freshman in college. I applied to Harvard last year with a 34 ACT, 5th in a graduating class of 450, 12 season athlete who ran 54.01 in the 400mH and 49.38 in the 400. I was not accepted to Harvard. I was waitlisted at Brown. I was accepted by Cornell & Williams but they didn't jive financially ... also was accepted to Wesleyan which I'm not sure on the % but is also pretty low.
Point is... it's sort of a cr*p shoot to an extent and you really need to have an amazing application.
Good luck!
PS; Remember that doing well in school doesn't always mean your kid wants to go to an Ivy. It's a totally different environment and the academic competition has to be something your kid wants.