If you were my dad, I’d want to choose a bunch of stuff myself using Japanese Amazon and have it delivered to one of the Lawson convenience stores at Narita or Haneda for you to pick up for me.
If your kid is studying Japanese I’m sure she’d be able to work out how that’s done. I’m almost certain that you would have to go landside to do this though.

Of course, I’d like an additional bag of treats from you at the airport (although the queues at some of the airside shops that sell them can be epic, it depends on who is also flying at the same time).