I had an exterminator friend tell me that mice enjoy chewing spray foam, so only use the kind with fiberglass in it. Not sure which brands, but not regular Great Stuff.
You might want to consider laying a piece of 1/2" vinyl board along the floor and nailing it into the plate. Not sure if it comes in 1/2" but you could rip some 8' 1x's into 1/2" strips. Waterproof and quite chew resistant.