Fun in the ER

I was asked a question by a parent yesterday that caught me off guard: "Is this one of the first lumbar punctures you've ever done?" And I answered honestly (though sorta lied by omission): Yes. She certainly didn't have to know that her son was the recipient of my very first LP. Sure, I tried to make it look like I'd inserted thousands of long needles into young kids' spines before, but I don't usually hide my panic well. When I had explained to her why her kid needed one an hour earlier, part of my explanation was something along the lines of, "Don't worry! Dr. Attending has done millions of these before!" even though I knew full well I was going to be the one doing it. I couldn't very well have said, "Actually I'm going to practice my first one on your eleven-year-old. Don't be alarmed! I passed my anatomy of the back exam."
[side note: When she asked me that question I had a flashback to the very first Kaplan SAT class I taught, in which one girl asked me if it was in fact the first class I had ever taught. I went with honesty and told her yes: bad idea. I lost them. I might as well have written on my forehead: DON'T RESPECT ME, I'M NEW HERE.]
I mean, parents have a right to know when semi-competent medical students are learning how to do invasive procedures on their loved ones. However, if they truly knew, no one would ever consent to that. Right? I feel like if it were my kid I would have said, "No way! Dr. Attending will be performing this procedure, thankyouverymuch." It's been pretty well-documented that patients receive better care at teaching hospitals (ones with residents and students), but that piece of information seems quite abstract and theoretical when you're in a place like the one I found myself in yesterday. I do feel kind of guilty that I didn't come clean from the beginning and make sure she knew I'd be the one doing the procedure, but I also am pretty sure she would have said no. So what to do??
(p.s. Tap went well. Kid lived. Clear fluid. Discharged home.)