Valet is a per day charge, not per use. If you are requesting your car from the valet, typically they will put a Mickey head lanyard on your rearview mirror. This indicates to other valets that you have already been charged for the day. So you can take the car from the GF and valet over at the BW if you like without paying another $10. The only thing you would need to concern yourself with is the tip.
Channing, thanks for the review of your trip. I think it's just the law of averages, that every once in a while, the trip isn't perfect. We loved using Southern Elegance for our Disney and
DCL transfers. I thought the drivers were extremely courteous and professional. Hopefully what you experienced was the exception and not the rule.
CRFan, just noticed in your signature that you're going to give the GF a try. You, your mom and your dad should plan on walking over during your Poly stay. Maybe if it's not too busy, a CM can show you a room to give you an idea of what you'll be getting. Sugar Loaf is definitely going to be very different than what you've experienced at the Atrium Club and Poly Club though.