wide grin
broad grin

The doctor looked up and broke into a wide grin.

He gave her a wide grin, as if they were partners.

When he next caught up with me there was a wide grin on his face.

I looked her way, and offered up a wide grin.

I managed to get hold of myself and gave him a wide grin.

He saw that the men were watching him with wide grins.

He nodded his head and gave the children a wide grin.

There was a wide grin on his face as he stood.

The next time she looked, he gave her a wide grin.

"I understand you two know each other," he said with a wide grin.