victoria is the wrong side of london. l'st will be your station, the nat hist and the sci museum are both round the corner from south kensington tube sation. you can get there on the circle linefrom L'pool st. station , i think londoners correct me if i'm wrong.
Circle Line to South Ken. should be fine - suggest you each get a one day travelcard for Zones 1 and 2, and then you can call in on other places if you have time. see http://www.tfl.gov.uk for london transport info - the online journey planner is quite accurate in my experience.
If you're doing the nat history and science museums, suggest you pop into the V&A across the road if you have time.