I think the problem here is the poor advice they were given saying they couldn’t book a bassinet seat until 24-48 hours before departure. This is nonsense. There is no restriction on when you can book a bassinet seat provided you have a baby. Close to departure, non-baby having passengers can book bassinet seats with the caveat that they might get booted out in case a baby turns up.

So it may well be that other passengers with babies got better advice and booked all the available bassinet seats, in which case OP’s friends are out of luck. Poor showing by whoever gave that original advice.