Thanks Sir Duke and 3Boxers!
They always go out separately. I don't take them out at the same time. The only time they've been out at the same time is when we came home from the vet and my daughter had one on one leash on one side of the driveway and I had the other on another leash on the other side of the driveway.
The leashes we use are short, 6' leashes. I think the pulling on the leash is (especially with Loki) because he wants to explore the whole yard (1/2 acre) to find the perfect 10 blades of grass upon which to eliminate. Apparently just any blades of grass will not do. They must be the right blades of grass and they must be in a completely different area of the yard that the two previous eliminations. LOL
At night they're all business. Go out, pee/poop, come inside, go in crate, go back to sleep.
During the day all they want to do is play. I'm beginning to wonder if taking them outside for some play time, after they've gone potty and come back inside would help, or just make them want to play outside more?
With the piddle pads - does it confuse them to be trained to the pads and then to be re-trained to outdoors?