I'd go with 11E/F as you won't have any foot traffic and maximum privacy. As you said, you do chance being a few feet closer to the bassinets in the front of the economy cabin. If this is a concern, then go with 9E/F. I would avoid row 7 due to proximity to the lavs. Probably won't be an issue, but you never know. You'll experience very attentive service wherever you are, but there is a chance that they may be out of your first choice when seated anywhere in the rear cabin. If concerned, you can always pre-order your meals. The smaller J cabin on the 773 is a great place to sit, IMO.