Some of them have USB input. this would be good, because you could send over a new USB stick every 6 months or so full of pics and she could just plug it in (with instructions from you)

don't skimp on the resolution. it's only if your resolution is too low that the pics look pixelated. resolution is indicated by number x number (e.g. 1280 x 1024). it indicates how many dots wide x dote high make up the picture.

you can get battery powered, but plug in is probably better. you should be able to get adaptor or a plug suitable for UK.

i think its a great idea.