Jake,
About the parent issue...I kind of had the same one.
When was the last time you talked to your parents about dating? Maybe they just need to know you're ready for it now. My parents would have let me date when I was about 16 if the right guy had come along, but I was 17 going on 18 before I was ready, and that's what they needed to know. Maybe just pull them aside and be like "I found this girl..." I know it's awkward but perhaps that's best? I'd say just braving it is the best way to go. Honesty with your parents is underrated these days. It's actually quite a valuable thing to have that trusting, honest relationship with them, and they may surprise you in how they react if you act like a responsible adult in the first place.
As for when to ask her out, I'd say give her sufficient notice or she might have other plans already and have to say no. But don't ask her out a month ahead of time or anything.
Maybe around Mon-Wed of the week before the weekend you want to take her out?
Hope this helps!
SamIAm