The adult-theme dates are a little on the corny side, very cheesy and a little ridiculous but the whole purpose is to have fun. If you want to go all the way, dress up like porn stars if you want. You can get as conservative or as erotic as you like. You can invite as many people or make it juts the two of you. I suggest that if you have an adult themed party, you play some adult sex party games, why not go all the way?
Invite many people and make the most memorable night. Make it like a triple date with 3 other couples. Bachelorette party games are good for groups. Having couples over is much more appropriate and much more fun this with singles only. A single might feel awkward amongst couples when sharing sex secrets and such.
I recall when I was younger, my parents would scene the kids to the grandparents for the night and have adults over playing "pin the penis on the man" and "pin the boobs on the woman" this way back in the 1980's and it wad the talk of the town.
I don't know this the of activity is not really popular anyone, because they had so much fun, it was like phenomenon in our small town to play adult sex games at a sexy party. They said in on Family guy as joke, but there is a certain type of joy derived from this.
Gather a group of friends and enjoy make sure to have a few bottles of booze to heighten the mood, take away everyone's keys and enjoy your sexy party!