Does Aer Lingus have kiosks to print boarding passes at the airport? If we're traveling in Ireland for a day or two, likely at B&B's that might not have computers and printers, we'd likely want to check-in online at T-24 but not physically print the BP.

Is a Visa Electron card basically just a Visa card...or something else?

Basically it's starting to sound like Ryanair is a pretty mean-spirited airline to fly. Make one mistake and you either have to pay 200-300% of your ticket price in fees or you're stuck not flying. I don't mind paying reasonable fees (begrudging accepting a baggage fee as "reasonable") but I'd worry a lot about "gotchas" that I didn't expect once I got to the airport.