First of all, good for you for training your small dog. So many people don't bother.
Second of all you are right to recognise that while he may behave perfectly at home, he will need practice with distractions. Do you know of someone with a well behaved dog that can help you set up situations for training. What you want to do is have a friend with their dog on one side of your yard (or other controlled environment) and take Miles to a point where he is interested in the dog, but the dog is still far enough away that he's not getting overexcited. Give Miles his command and make sure he does it. Do not let him get away with not listening, so if you have to gently place him in postion and hold him there then do that. Praise him though like he never needed your help. His reward of course will be playing with the dog since that seems to be his highest motivating factor. After a few minutes of play go get him and repeat the exercise. Since he likes other dogs so much he should fast learn that by obeying you chances are high he will get what he wants.

Good luck!