OH lord, please don't do that. No parent in their right mind would do that, because it's obvious what would happen that night. You're seventeen so I know you may think you're in love, but please try to wait.
If a guy loves you, he will wait for you. You're still under the age of eighteen, so you really shouldn't be sexually active. If you are, please use birth control and/or condoms. Don't believe in the pull out method or anything other than birth control.
I would not ask your mom. I'd worry if she'd even consider it.
If my son asked me that, I would be livid.
Have fun at prom. Make good choices! :)