Based upon our experience last year, in a similar but slightly different situation, we purchased two international tickets and paid lap fee for infant. The adult tickets were automatically ticketed (within an hour or two), but the infant was on a separate record. We were told that it had to be manually processed, but once it was they would move the infant onto our tickets/records. It sounded weird but was apparently a limitation of the computer system? About two weeks later the separate "temporary" record for our son disappeared, and he was on our ticket. We booked these flights 3 months before travel so perhaps they prioritized work based upon date of travel?

We did redeem some international award travel at the same time for the three of us, and those were all done on the same record...