Tried searching using the words "new members" and "retroactively" and could not find any. Two adults and two children flew DL from BOM to the US and returned on AF to BOM. At my suggestion, they opened DL accounts just before the departure. Since one cannot open accounts for those below 13 online, it had to be done manually and was completed only after they returned to India.

I added the adults FF# to the flight before the return and somehow they got credit for the outbound as well which was more than 30 days before creating the account. For the kids, I had to claim mileage retroactively and they did not get anything for the outbound. Is there any way around this?