To be honest, unless you're up for the idea of installing some sound editing software, and learning how to edit out blank spots in the recording, chop the waveform up into individual tracks, exporting the audio and encoding it to mp3... i'd recommend just downloading the tracks. If you already have them on tape, it isn't copyright infringement, and if your son can use an mp3 player i'm fairly sure he'll know how to install an application to download songs from the net.
I say this from experiences I've had trying to teach various family members and family friends how to do this (from vinyl, same process really) and having them completely not grasp the process, despite repeated explanations. Downloading the tracks from the net is really much, much easier. (make sure you disable the client's upload feature though, to avoid legal problems)