[Marilize]

It's much easier to teach him something new than to untrain him not to do something else. Teach him the new way, but only remove the pee pad when he gives it up and reliably goes outside.

Moving his potty spot outside is totally possible and I did it with two of my Yorkies, but it's not as easy as starting outside. Dogs become conditioned to peeing whenever they feel a certain texture underneath their feet or when they smell urine/ammonia. If he's attached to the pee pad and you remove it too quickly, he'll start peeing on your carpets.

Get him conditioned to grass before you remove it. The easiest way to do this is to spend lots of time on grass, especially on walks. Little boys like to mark their way around the neighbourhood and this gives you a great opportunity to take him to appropriate grassy spots and encouraging him to go. Take him out regularly and consistently and he'll be trained to grass in no time.