You are the established people--the onus is on you to reach out to them. I think that *is* a set rule.
(In Jane Austen's Price and Prejudice, Mr. Bennett goes to welcome Mr. Bingley to the neighborhood.)
So swing by and say hello. Bring something as a welcome gift if you can.
(I love that card w/ the names of everyone in the house, and contact info perhaps. Or maybe a list of all the nearby vendors you use and recommend--dry cleaner, handyman, plumber, which grocery story is best for what, etc., nearest park for kids vs. dogs, that sort of stuff.)