Stories i would like to see are from the male perspective with some reluctance on the woman's part but nothing violent.
Son and mother play Truth or dare, or some similar game, with others that leads to unplanned public incest.
Son gets mom to pose for pictures and gets her to do more and more. I have read a few really good ones with this theme but can't seem to get enough of it.
Strangers on the beach end up having public sex. Additional points for anal, bbw, rimming and definitely people watching.
Son serves woman at cfnm party and his mom shows up, neither expecting it. Maybe prostate play involved.