No problem. If your wife is asked, she may want to have a story lined up about why you are not there, since throw-away ticketing is frowned on, and it is a little unusual to have a family minus father flying back from holiday.

In theory, but never in practice, they could charge your husband the full one-way fare for the outbound. (Note: I am not a fan of this insane policy airlines have, and have posted frequently about it.)

I would say something like "...he's running late in a taxi from a meeting in his office...hope he makes it."

Enjoy the trip!