The first thing you need to to do is find out what they mean by field rendering. Do they want stills at twice the frame rate so that they can do their own interlace in After Effects ? If they want interlaced stills at the frame rate ( i.e. 29.97 ), which field is first ( even or odd, or for some systems 0 or 1 )? Once you have that information, the setting you are looking for is in the Render:Output Tab. You select none, even or odd from the dropdown menu. Whatever you do, be sure to send a test file before you send anything vital. The even/odd information you get can be wrong ( sometimes even the manufacturers get it wrong).
For a test file, I recommend a ball going from corner to corner at medium speed.
Hope I helped.
Jay