The last time that I checked, the University of Pennsylvania had about a 6% acceptance rate. I would expect that the percentage of applicants who are academically qualified to attend is probably in the 80%+ rate that is typical at other top universities. Assuming that you do not have a Nobel Prize and that neither parent is the leader of a medium sized country, the University of Pennsylvania is a reach for everyone.
I do not think that I would worry about two B’s. Just do the best that you can, keep your budget in mind, make sure that you apply to at least two safeties that you are comfortable with, and you will do fine.
By the way, one daughter had three B’s in high school, and is currently studying for a DVM in a highly ranked and very good program. The B’s did not stop her from accomplishing exactly what she wanted to accomplish. I do not think that a couple of B’s will stop you either. None of us is perfect.