My spouse graduated from Penn and is a part-time professor there. My son is a junior now and really likes Penn. No SAT or ACT scores but he did pretty well on PSAT. However, his grades aren’t stellar and not a lot of ECs. He wouldn’t get in regular decision, I’m sure. But I wonder if he has a chance of getting in ED. Do they give any extra weight to being a child of PT faculty, plus legacy?
Legacy yes, PT faculty not sure. Do you live in Philly and does your son attend a public high school there? That is a boost.
No. Northern VA public HS. No boost there, I’m sure. 
Legacy only counts in the ED round at Penn. Not sure if being the son of a faculty member helps but I guess it can’t hurt. But none of the “bumps” will get a candidate in who is not academically qualified in his/her own right.
Read this article. Looks like Penn admits about 60 fac-brats each year out of a class of 2400:
http://www.nytimes.com/2005/01/16/education/edlife/the-other-legacies-fac-brats.html
However can you clarify if your wife’s part time status entitles your child to the tuition benefit?
Nope. I happened across that factoid in googling. Have to be FT. Thanks for link!
If your wife is not eligible for the tuition benefit then I doubt your son will get any fac brat advantage. But it doesn’t hurt to try.
Re-read @happy1 's comment: