If you are going to arrive first, one suggested meeting point is the lobby of the Sheraton CDG, which is located practically right atop the TGV/RER/CDGVAL stations.

As JOUY31 has stated above, the AA passenger, once he/she has cleared immigration, can proceed from 2A over to the meeting point. The entire distance is indoors and part of it is served by moving sidewalks. Baggage carts (if needed) can be easily used.

More on the CDGVAL (including a simple map):

http://www.easycdg.com/pages/cdgval_light_railpag.html