I'm You're Mommy Now

A long time ago my now wife and I took a family trip with my Mom, and sister. We stayed in the same room as my mom. After a long drive my mom took a shower, my then girlfriend and I started to get frisky on the bed, it got a little hot, and when my mom came out we stopped, but she knew what we were doing, our faces were flushed. We went outside in the back of my mini van and started back up. I said "what if my Mom comes out?" She grabbed me looked dead in the eyes and said "I'm your mommy know." I was so turned on I closed the trunk, and fucked her. We popped out when we were done, looked across the parking lot and made eye contact with some other motel guests, they dropped their gaze and turned away.