OK moral dilemma. every year girlfriend and I do Xmas markets. this we are off to Prague with toddler. since this was booked my partners 16 year old daughter has got 17 year old boyfriend . she is staying at ours with my 17 year old daughter while car are away. my daughter goes to college so is a potential period most days for five days where in theory said step daughter and boyfriend could be alone at ours. it is worrying me to the point I don't want to go. what do people think? am I untrustworthy and over reacting or being sensible?