I've never been myself but my sister has several times. She prefers Beuna Vista as she says its more like a self contained resort and everything is on hand.
Might be worth looking into if your mum doesn't want to have to hire a car.
They would like to hire a car, but when you are over 80 it's a hassle trying to rent one unfortunately. Not sure they would be safe anyway, with driving on the right etc...