Gulfboy has given a very full account of the joys of Bahrain, though his account of the Tree of Life hardly does justice to just how underwhelming it is!!
The exhibition house at the Durrat Al Bahrain development is interesting for showing the grandiose scheme planned for this southern part of Bahrain, and it is only 90-120 mins round trip from the airport.
The Museum is supposed to be very good value, and the Grand Mosque also has a good write up.
Failing that just lounge by the pool at the Movenpick.............there isn't anything else to do at this hotel.
The Visa for a Brit to enter BAH costs 5.00 BD if GF do not pay it for you, and there is a Bureau de Change just before Immigration.
On arrival if your mother contacts the BAS Handling Agent staff at the Transfer desk they will advise and arrange any free hotel accomodation etc.