Thanks for your replies!
Currently considering the A-10C and Flaming Cliffs 3 (which I have and like). He's a huge Bf109 fan, so will get him that module, although the wonky damage model worries me a bit.
How would I go about gifting him modules on the website and not on Steam?
Also, does anyone know whether DCS will have a sale soon? I'm actually planning to get most of the modules next time, and would love combining it with the gift for my buddy.