When we visited Barcelona, we wanted to stay in a nearby place, so we chose Premia de Mar, and I must say that its beach was the highlight! We were there at the beginning of November, by the way.
The beach is very, very clean, and we enjoyed numerous beautiful walks there every evening. The playgrounds are very safe and such a necessity for parents.
We didn't mind the railroad at all; in fact, it just added to the charm, in my humble opinion. If you don't want sand in your shoes, there's an asphalt trail that is well-lit at night, and the views are simply beautiful.