one other tip...
When travelling as a couple, I always try to book on an aircraft type that offers two seats together by the window. If you go on a 747 you will have a third seat next to you which will probably be filled.
Choose an A330/340, 777, DC10 or MD11 if you can. Virgin's afternoon flight to LA is an A340 so you'll get more privacy. United have 777's in 2+5+2, but some (Continental, BA) are 3+3+3. Not sure about Air France.
The good thing about online seat selection is that you can do 'odd' things that you couldn't do face to face at check-in. When travelling in a set of three seats, I usually request the window and aisle seats, leaving the centre one free. That way it's less likely to be filled if the flight isn't full. Then, if someone turns up to take the middle seat, simply offer them the aisle instead and you've lost nothing (they'll be grateful). If the seat IS empty, you get to stretch out!