AA is pretty strict on ORD being CLEARLY an origin or destination, and absolutely NOT a connection. They look thru the flight activity & PNRs as needed to confirm that when a problem arises, a trip doesn't post, etc.
So, you have to think on completely separate PNRs for this. Book that whole itinerary as one trip and you'll get nada as far as the ORD promo goes. Book ORD as an origin of one, a destination of another, then that's a diff. story.
It's totally different than the recent DFW promos where you could use DFW as a connection.