It’s great that your parents are supportive of your plan! But if you are self-conscious or otherwise concerned about them hanging out while your partying, they can always drop you off and head 8 minutes up the street and have fun at the casino until you are done. The only issue is that I don’t recall is whether the cell coverage at the Ranch is any good, and whether you can easily text or call your parents when you’re done.
Also, depending on the time of day you plan to go, they could easily hang out at the bar. When I was at Sheri’s last year in early September around 11:30 am, there was just the friendly bartender and some locals grabbing lunch inside, pretty tame and low-key. Your parents already sound pretty cool for driving you over, and as long as they aren’t too prudish, they might enjoy hanging out at Sheri’s while they wait for you.
Lastly, keep in mind that nothing it actually free, and I believe if you use the limo, the driver actually gets a cut of the proceeds from the party, so the courtesan negotiations may be different if she knows she has to tip out to the limo driver.
Good luck on your trip!