[Grammar] American English usage: He’s (the) nicest when he’s with children.

[sitifan]

1. He’s nicest when he’s with children.
2. He’s the nicest when he’s with children.
3. She works hardest when she’s doing something for her family.
4. She works the hardest when she’s doing something for her family.
In British English, #1 and #3 are acceptable but #2 and #4 are not.

Are they acceptable in American English?​

 

[Tarheel]

Yes, and you could also say "He's at his nicest ..." and "She works her hardest ...."