You fly side by side, not together
Each of you flies with your own pilot. With two pilots launching in sequence you are in the air at the same time and often within sight of each other, which is what most couples want.
Photographs of both of you
Ask for GoPro coverage on both wings, and tell the pilots you would like shots of the other glider. This is easy to arrange in advance and impossible to arrange mid-flight.
Booking privately
A private slot removes the wait between launches and lets the pilots coordinate. On a busy weekend that is the difference between flying together and flying an hour apart.
Late-day flights
The late-afternoon slot gives the best light, but it is the most conditions-dependent. Have a morning as a backup.