Can't speak for Canada, but here's what you'll need to re-enter the United States.
Passports are the best ID at the Border.
Second best is a Government Issued ID with a photo, like a Driver's License
. AND your Birth Certificate.
For the Kids, a Birth Cert and School ID is fine.
Dogs should have a Vet card, but in 11 years I've never checked.
and proof of insurance on all vehicles.
The Lynden/Aldergrove border crossing is the best one to cross at right now. It's open from 8am-Midnight.
If you take the Guide Merdian Exit off I-5, be aware that construction is going on while they widen the Guide.
A good detour is to go a bit farther north to the Birch Bay Lynden Road and then go east to Lynden and the Guide Meridian.
There is work going on at the Blaine Truck Crossing and work will start in Sept on the Peach Arch Crossing. Expect delays at both crossings.
Last cheap gas is at the Safeway and the AM/PM on the Guide Meridian. Both are about 3 miles south of the Lynden Crossing near the Birch Bay Lynden Road. Gas is around $4.00gal in Canada.
Coming back into the US.
No Beef, Lamb, Citris or Tropical Fruits.
Locally grown fruit in season is OK.