You typically can add this information to the booking later once the gift has been given, but if you include their frequent - flyer number
on the reservation it is quite likely that the
flights will show up in their list of
upcoming trips in their airline account and may even land in their inbox.
Likewise, if you have a bunch of different kinds of miles you can draw from, it is more likely that you will be able to find miles that you can use to book
flights based
on the current availability for your
upcoming trip.