Mary2e,

Mrs. LawFlyer and I do this all the time on CO 10 from IAH - CDG. On trips when my firm pays only for my BF seat and I cannot get a OnePass BF seat for my wife (when she does, indeed, want to go with me), then we'll either buy a coach seat or use OnePass miles for a coach seat, and usually switch halfway through the flight (or after the meal, or whatever).

Maybe I've done the "wrong" thing, but I have NEVER asked the FAs in advance for permission to do this. It's true that I usually know several of them in the BF cabin every time I take this trip, but my wife says no one has ever questioned her being up there when I go to the back.

Also, when we are traveling with 3 young boys, one of us often takes our "tour of duty" in the back with them while the other gets some sleep up in BF -- then we trade out. Maybe we've just been lucky, but I've never had a problem with it. Very occasionally, we've gotten a strange look from an adjacent passenger, but who cares! Being unobtrusive and polite goes a long way -- and it sounds like that's exactly what you are planning to do.

Good luck!! And have fun...

LawFlyer