How did you book next summer with the AARP discount? I thought it was only valid for flights through March 2016...
Just worked for me. Clicked through on the AARP from Dan's link, and searched for dates over Jul 4th weekend.
I didn't use the 10% off, but the 30K avios instead.
Also, couldn't select 'business' from the search page - just 'economy', but 'business' column showed up on the results as well, with the appropriate discount.