Things to consider on AA reward bookings:
1. AA or BA: The BA fuel surcharge on TATL flights will cost you a lot more. If you fly AA JFK-LHR and then take the train from London to Scotland it will take more time but save money. Even if you fly AA JFK-LHR then connect to BA for LHR-EDI you'll still get hit with surcharges.
2. UK Air Passenger Duty (APD): APD applies to departures from the UK. The APD for flying business from LHR-JFK appears to be about USD 100 more than if you returned in coach. Fly business on the overnight JFK-LHR but consider whether it's worth it to you for business class on a daytime LHR-JFK return.
Play around with these options on the AA web site.