Thank's to your post I realized I had a similar issue with 2 separate booking on AZ, at first I thought I might have lucked out because I had all tickets issued on DL stock (it was a mixed itinerary of AF & AZ) So I thought I would be able to get this solved quicker, But after being over an hour on the line with several rep's seems like they have no clue what I am talking about, all they know is that the Inft's are ticketed and good to go, they know nothing about caps for the amount of infants on a single flight.. although I already confirmed with AZ that the inf will not be allowed on the flight (even though the inf tkt was already issued) DL just doesn't know about any ssr requirement etc.
Any advise, any contact info for DL department with agents that have some (basic) knowledge..?