It has always broken my heart to learn that no DAW is easy to learn or easy to use. I find it inexcusable. I come from an audio production background (back when we used splice blocks to do edits), I'm a musician, and I'm an experienced software developer so I doubt it's because I don't understand the technology or the workflows.
The closest I've come to a DAW that was easy to learn and matched a pre-MIDI workflow was Cubase. Even that, however, had frustrating quirks that rendered it unrecommendable. Trying to figure out audio routing, trying to get my MIDI controller keyboard working the same way each session, and setting up drivers to work with the hardware ADCs made it a lothesome experience (although admittedly, some of that was because I have little experience with Windows, and you need to be Windows-savvy to use Windows since it lacks discoverability for common tasks). I've also tried Linux-based DAWs (Rosegarden is very good and definitely in German) but signal routing in Linux is even worse than Windows.
It just may be that what your Dad needs is not a computer DAW, but some audio hardware that will let him do what he wants and get on with the job. If he's not going to be doing loops and samples and beats, autotuning, or MIDI sequencing he's probably better off with an old 8-channel mixer. Then again, once the (steep) learning curve is past, he'll be able to do so much more with a DAW. Any DAW.