One thing to bear in mind is that if you are using the bassinet seat in F on the 777 you can't use the IFE too (unlike CW). Also, we found our 3 year old to be at the lower limit of likely suitable age range for F due to being quite far away from us (was in a middle pair). He had done quite a bit of flying and my wife just felt a bit uncomfortable about not being able to easily reach him during take-off/landing (although he was basically not bothered in the slightest!). The CW middle pairs are really ideal when they are quite young.

Having said that would do it again, especially if you have availability on a flight to SEA! (Definitely call an open office, don't wait!)