I thought " fornicate" Might work, but that seemed too judgy.

为用“私通”可能没事，但这词带有评判的意味。

Andrew, Danielle, daddy's going to fornicate for us! -Just keep your voice down.

Andrew，Danielle，爸爸要在们面前通奸了。-小声点。

A bunch of booze-drenched hill people just sitting around in their underwear and-and chasing rats and fornicating in the stairwell.

全身酒味、穿着内裤乱跑的，追耗子的，还有在楼梯口就搞起来的。