Brent,
I have driven back and forth over the border to many times to count and never had a problem. Do not have any weapons of any kind, declare everything you should (Booze etc). I have never been asked for registration (they know if it is registered and who too as they have camera's looking at every angle of the vehicle and computers checking all kinds of items (including if you have a record or outstanding warrants etc).
As it has been said make sure you have your passports (you can even get a passport for a dog or cat if you have one with you) LOL!!!
Have a good trip,
Stewart