If you want trains in alexandria, just go sit at the train station, its always busy. The nearest hobby shops worth visiting are Sidetrack Hobbies in Leonardtown, MD, or the above mentioned Catoctin Mt. Trains. Both are about equidistant, in complete opposite directions.
When I lived down there, the Union Street Public House was good for fish & chips, I'm sure it still is. There's lots and lots of restaurants along King St. and the side streets, you should have no trouble finding something.
