We got a tandem for our 20th wedding anniversary back in 1975. Now celebrated our 54th (yes . . . we are THAT old!) and still manage to get in a 100 miles a week. So far have tandemed TWOgether for 225,000+ miles.
You sound like nice kidz . . . . happy anniversary to your folks!
Pedal on!
Rudy and Kay/zonatandem