Facetime is never as good as the adverts suggest. Your relly will be wondering why you keep turning into coloured blocks and probably call the police. If you understand the technology, you just know what it is doing, but if you don't, a flaky connection can be weird.
If their house has a really good 3G signal, then one with a mobile contract will do the job - but £30 a month or so.
As to type - an s/h iPad is a good idea because they just work, android is occasionally weird and you don't want weird. Get the last generation device, not something ancient. My mother (who is the most computer phobic person on the planet) can drive an iPad reasonably easily.
As above, all this gives you is facetime and internet connections. Not sure if this is what you really want.