Safety in the core part of Paris is pretty much a given so I wouldn't worry too much about that too much, proximity to metro, bus and restaurants/cafès should be your main concern. Metro station Strasbourg Saint Denis has lines running both north/south and east/west which is really ideal. The placement in the 18th is less than ideal from a touristy point of view both in proximity and transport.
Based purely on proximity and transport I'd go with the Rue d'Enghien without question. Rue Lamarck is long (for a Paris street) so it's harder to say but while Lamarck - Caulaincourt is picturesque and uniquely Parisian with kids the charm is probably less important than practical matters.
My $.02, enjoy Paris,
=Tod