I ride with one of my dogs beside me all the time and it's perfectly safe if your dog is trained. You have to use a proper bike attachment like the 'walky dog'. You should NEVER try and ride a bike with your dog hooked on a leash. With the Walky Dog the dog cannot reach your tire and the spring on it keeps them from yanking you down. But my dog Forrest is a large dog and I wouldn't recommend trying to ride with a small dog. I don't think he would be tall enough. But I bet your baby would love to jog with you. And as far as how long he can go it really depends on him. Just keep a close eye on him and see what works for him
He'll probably suprise you!