If I understand you, you mean they won't play down under. That's because they are probably region 2. Australia etc are region 4. Now there is no physical difference, the whole region thing is merely a commercial thing. Anyway, pretty much any DVD player can be "hacked" into a region 0 player (ie any region). The grand kids should write down the exact make and model of the player, go to a site like this and obey the hack instructions:
http://www.dvd.reviewer.co.uk/info/multiregion /hackable.asp