In the spirit of "DoTheSimplestThingThatCanPossiblyWork" don't try and reinvent the wheel here.
Run with some easily commercially available and stable platform (EG iPad is a fairly universal thing, decent build quality, known form factor, etc.) as your job is not to invent some new hardware platform but to make a kiosk that presents some content. You cannot make a small-volume touchscreen kiosk device for less money than Apple of Samsung can sell you a tablet or even full blown laptop or desktop computer, and you will waste huge amounts of time & money trying (and no-one will thank you or pay you more for doing so).
Doing it in a web browser (HTML + JS + video) locked in kiosk mode means your software/content, such as it is, can transfer to almost any other device with little effort.
Edit to add: Because it's relevant, and because he's a hero, check out Tim Hunkin's website, he's made all manner of interactive kiosks, displays, and arcade machines and has some good insights. My favourite being the dog walking simulator.