I'm guessing no one knows how to respond Susie.
I dont either, but I think the question is if a floppy disk is necessary on a keyboard? Some keyboard models do have a floppy drive to transfer data between the keyboard and a computer. Often that data is a MIDI song (and you might be transferring it in either direction). Or sometimes it is new accompaniment styles for those models that offer accompaniment. I think the data is sometimes play-along song lessons, but I'd guess that aspect wouldnt be much interest to a 3 year student.
If that data transfer is of interest to you, you surely can do it via the normal MIDI interface too, using a cable connection to the computer. I'm really hesitant to say much, because I feel sure it is a matter of personal preference, but I'd guess if you have not needed it before, you may not need it now either.
Seems to me like there are more important features to decide which keyboard, like weighted keys on a digital piano, and good sound, and you mentioned many voices, and perhaps you meant it should have nice wooden furniture too, etc.
Floppies are less popular on new computers, as they are small and wont hold much data as compared to other media. So new computers today are less likely to even have a floppy drive.