Good suggestions everyone! I'll pass them along. All I could think of off the top of my head when they asked me was "uhh...lab?" and most labs I've met are pretty energetic.
This is actually for a family involved with the GSD rescue that I volunteer with. I think this family is going to go for a rescue dog either way, not a breeder dog, but based on their criteria, willingness to work with the dog and a few other things, I wasn't sure that a GSD would be the best fit. I actually recommended that they look into an all- or mixed-breed rescue, so that they could find their perfect dog without giving too much consideration to breed. A mixed breed like Lies' Coke would be perfect for them.
Like most novice dog owners, they originally wanted a (GSD) puppy, but after some chatting, they decided that an older, more mature dog would probably be best. These are great suggestions, never would've thought of them myself since I work almost exclusively with working breeds. I'll send them over, along with the Petfinder links. Thanks all!