"The bathroom is behind them."
No alternatives to 洗手间! There are so many synonyms and euphemisms for 'toilet' in every language it is clearly impossible to cover them all, but we really need more than 'hand wash room'. This is to my mind too euphemistic.
Suggestions for inclusion:
厕所 Cè Suǒ (Toilet)
卫生间 Wèi Shēng Jiān ('bathroom' or lit. 'Hygiene Room')