What major(s) are you considering? No reason to choose bio at UVA if you don’t think that department is great (but I wouldn’t rely on 2nd or 3rd hand reports.)
In the big picture, pre-med wannabes should major in something they like, and attend a school where they can be at the top of the class. Pre-med will be challenging and a grind at both of the schools on your list. For this and other reasons most incoming ‘pre-meds’ do not end up going to med school.
You can take out a max of $27K in total loans during undergrad. Anything beyond that is on your parents, either directly or as co-signers. I would not recommend your parents assume any debt for WashU unless it would not change their lifestyle at all, or impact their retirement savings. Further, if you do make it to med school, that will likely be paid 100% with loans…so minimizing undergrad loans is key. Also look at this thread for further information about the Grad Plus loans: Bill Introduced in Congress will eliminate Grad Plus loans