While I agree with everything BDEMARIA says, if I were in your shoes, I would opt for F. While J is nice, F is a much better experience. 36 nice seats vs 16 very nice personal pods. better service with greater comfort. This sounds like something of a "special" trip, so make really special.
To me, this is a no brainer. You're total time in the air is ~ 19 hours, the availability in F is there, the extra miles aren't many and you've got plenty to burn, you've never been on a 777, and you're wife has never been in F.
At the end of the day, and after a few hours in the air, I wouldn't want be in J looking forward and thinking "For a few extra miles, we could have been up there". Not to mention what my wife might be thinking.
Go for it and enjoy your trip.