The train to Barca is really worth it. Not sure about Girona though but I would imaginethere will be excursions or even buses as it does have an airport.

There are several ferry companies that operate up and down the coast, the services are regular and relativly quick and scenic.

train does go to gerona from SS on regular basis.
to get to lloret/tossa you change at blanes and get bus.
there are plenty of excursions to surrounding areas, including one to Estartit and medes islands-although it is long day out.
there are also bus trips to local water parks/markets etc
as stated above there are also ferries that go up coast to lloret/tossa and other resorts.

Thanks for your help.

One final question - a really naff one I'm afraid - do you know if Santa Susanna or Malgrat has McDonalds or the like, just as a back up for the kids!!

There is one there for the kids

There used to be a Burger King almost right outside the Hotel Riviera, not sure aboutr McDonalds, but there are a few in Calella

Llindy is right it is a burger king, always had special offers on when we was there,

Firstly there is no direct train service from Santa Susanna to Girona. You will need to change at Macanet which I think is the last stop and get a connecting service to Girona.
Secondly the Mcdonalds in Santa Susanna is set back on the main coastal road not far from the Santa Susanna Resort Hotel. The Burger King is by the Riviera Hotel and not so far to walk if staying along the main strip.