I am not an expert on this but I think regardless of the tools or platforms being used to organize the files, more important is likely going to be the MP3 metadata added to the files with date, participants, genre, comments, etc... so that you can easily switch platforms later and don't have to rely on saving some ever-growing database. Maybe you could also get the kids to give you a comment or quote to also add to the MP3 metadata.
The only platform I have used to organize and share music is Ampache [1] but that is likely overkill for your intended purpose. I don't know what the best tools would be to add the metadata to MP3 files however.