Lol. Well women are 10 to 13 feet tall, so not quite the size of a bus. In chapter 5, Luna sees 'mouth to mouth kissing' as the epitome of marital fidelity. Therefore, it's safe to assume French kissing another woman would be considered cheating.

As for sex, that may not have the same implications as it does in our world. While we don't know the specifics of a Healer's role in this soceity, we get the impression heterosexual sex has other uses, perhaps even outside of a monogamous relationship. Either way, that's an excellent question. If Luna and Ash would ever get outside the house again, perhaps we'd see some more answers to these questions. :)