Her father did give Theo and him a nod.  "Welcome to the U.S. boys.  I’m sure Hermione has explained to you how important it is that as much as you are  apparently  here to bother her friend, you are also here at the invitation of the President.  So please," the President’s concerned look moved from Theo and Draco to Potter and Weasley, "try to not break any laws, or end up in the news."