Agree with everyone else to check in at T-24.
Luckily this is T-24 from your first flight, not each flight, so you should still have a reasonable selection of seats as you'll get in there before no-status Y passengers flying directly from London.
I can see you took a decision to pay for seat selection which is wise if the money is worth it for you to remove the possibility of not getting what you want.
OLCI is still recommended in advance because it reduces your (small) chance of being selected for involuntary bump as you have shown you intend to fly.
You will need a document check if travelling to the US (check passport validity and ESTA).
Since you have luggage to drop off they should do it at bag drop in EDI.
Consider purchasing lounge access. It can make an occasion feel more special if you're not a regular in them.
https://www.edinburghairport.com/pre...lities/lounges
I find the food in BA Y just fine.
There are a number of free special meal options available for selection, but IMO none that give an omnivore significant benefits over the standard offering.
I agree with
flatlander that you're likely to feel more special with some of the hampers available for purchase in the terminal than the BA gourmet meals.
https://www.heathrow.com/file_source...rling-menu.pdf
https://www.heathrow.com/file_source...icnic_Menu.pdf
I'd probably regard these as an addition to the in-flight offering rather than a replacement.
There is a thread somewhere about someone taking on Wagamama ramen noodles but I've never been brave enough on a plane (have done it on a train).
You may as well go for these travel enhancing options because if you're treating your wife to a trip to NYC your wallet is already as good as broken
