Sorry for taking forever to answer this: I tried to answer back on April 8th but my account wasn't verified/working yet (I haven't posted on the forums before), and by the time it was I'd forgotten.
Regarding hitting Enter to log in: that does work in every supported browser: Chrome, IE, Firefox, Safari, and the default browsers on iOS and Android. It logs in using a bog-standard HTML form with a Submit option, so I'm not sure what more we can do there: it seems like maybe your virtual keyboard just isn't submitting the form normally.
Regarding logging in automatically: if you log into your devices using Kiosk level users, we have an option in Project Settings to not log Kiosk users out. You'll still have to log in manually once on each device, but after that (assuming cookies get persisted as normal on your devices) they should log in automatically.