I don't know that I'd make this offer, but I think the OP was genuinely being kind; he has empty spaces on his boat, it's a holiday evening, and he thought why not? (Sorry don't know if OP is a he or she, no offense meant). There ARE people who don't mind having their SO or family members around while they work. DH is a professor, and I've sat in on his lectures sometimes at his invitation. We have a niece who TOOK his class. My ex-BIL is a flight attendant for United, and when everyone was on speaking terms (don't ask…

he would encourage family members to take the flights he was working on, or even sometimes bid for specific flights he knew we'd be on. As a PP noted, entertainers are often given comp tickets for family members to come watch them work. While some of you think it's awkward, there are many who would think of it as fun!
And as far as it being awkward to share a cruise with strangers, have none of you ever taken an Illuminations or Wishes cruise by buying seats in someone's boat? There's a whole thread on the DIS about fireworks cruise availability. How is offering space to the skipper's SO- or her/him accepting it- any different than sharing a fireworks cruise with a stranger? Heck, I met one of my best friends via an Illuminations cruise. She had spaces, we wanted to cruise, and that's how we met, TEN YEARS ago. I've only actually seen her four times since then- once again on that first vacation, two days on a subsequent vacation when our dates overlapped, and once when they vacationed in Bar Harbor. I'm not saying that the CM's SO will become lifelong friends with OP, but it's just not as creepy and awkward as some of you seem to think!