We've been traveling and working non stop this summer. Europe twice in the last two months, plus five cities in the last three weeks. As a thank you my boss asked me to join him at a spa for a weekend of relaxation.
Have a wonderful time, if neither of you are married.
And if you are but not to each other. I think you are both just home-wrecking whores, but still by all means have fun, but for gods sake, put a bloody wrapper on it, and don't expect him to leave his wife for you.