A small thought... if your sister or her daughters have iPhones, with iOS5, Apple has introduced iMessage, which is a free text/media messaging service between iphone users (text rates don't apply). I haven't tried it yet, though, so I can't offer a review.

http://www.macworld.com/article/1629..._imessage.html

I recently replaced my limping, four-year old Blackberry Pearl with an iPhone 4s. I love it and use if for all sorts of things. It's quite handy for traveling, for instance - on my last flight, I checked in on my phone, received flight regular flight status updates, found out connecting gates, was able to access a map of the airport as well as lists of amenities, all on my phone.