Thanks - I actually did a whole bunch of tweaks after this was finished. When I get some time I plan to take another short video showcasing them. Part of the tweaks was to completely redefine the gamelist and get custom loading screens for each game showing the controls to use, and testing everything.
Basically I redid the entire software retropie setup from scratch. Those pre-built bazillion-game images are great, but this was the only way to get it to work exactly how I wanted.
It's now completely 100% user friendly and (so far) has proved impossible to "break" by the kids, and it has all my old favourite arcade games (and home computer/console systems). I'd say about 150 games total.
When I get half hour spare I'll take another video and link to it here showing what I learned and what I changed.