Yes, you can ride your bike with your dog. They have several devices out there on the market that can be attached to your bike so you can ride with both hands on the bike and don't have to worry about getting pulled over by your pet.
http://www.thedogoutdoors.com/ (is one example)
I would definitely train slowly and not go out for a 2 mile ride the very first time. I've seen a few people use these with some success. Others have problems because the dog wants to stop and sniff along the way and you either jerk on your dogs neck (I would probably use a harness with one of these) rather forcefully or your bike is pulled over and you fall off. Training is a definite must I would assume.
You also have to keep in mind that a 7 month old GSD still has about 10 months of growing left to do (not all in height, but also in muscle mass). These guys are very prone to developing orthopedic disease, and while there is no consensus out there yet, making your dog run long distances on hard surfaces can lead to the development of arthritis and other trauma to the joints, just as in people. In most dogs, they don't even recommend letting him or her jump until it's reached it's full size and weight so as not to damage the shoulders, spine or knees.
If you are having trouble keeping your puppy tired (and as everyone knows, a tired puppy is a well behaved puppy), considering getting some of those "smart" toys for dogs and letting your dog tire herself out by using her brain. The BusterCube, filling a kong with her dinner and freezing it, other treat-dispensing toys (just make sure she doesn't get so much food with this method she gains too much weight) can really workout a dog's brain and is an effective way to tire them out. Training sessions with the clicker (or other positive reinforcement technique) also help.
Anyway, just my 2 cents. HTH.