We both have passports, no big deal getting them.
The wife was adopted so her birth certificate is kind of screwed up.
If we can afford to travel, we can afford to get a document that lasts 10 years. Doesn't cost much more than a drivers licence in most states when you prorate it out.
We just came back from 4 months in Mexico,
took us all of 45 min. including waiting 35 min. in traffic, to cross into the US at Nogales. Matter of fact, Immigration just took our passports, went to the front of my truck, jotted down licence plate #, went to his computer terminal and entered something, handed us our passports back, (NEVER EVEN OPENED THEM), and directed us to the customs gate. Customs official went in our 5th wheel, petted our cats, took our cat food, except she let us fill a bowl so we would have a chance to buy new before we were attacked by the starving little buggers, and let us through.