I'm flipping through the channels and stop at something because the plot had Navy in it.

Cinderella Liberty

Peacetime sailor John J. Baggs is unable to get paid or receive new orders because somehow the U.S. Navy has lost his file. He is able to come and go from the base until curfew.
One night in a bar, he spots an attractive woman hustling guys at a pool table. He challenges her himself and develops an interest in the woman, Maggie, who turns out to be a prostitute living in a tenement with a young black son, Doug.
Baggs begins spending time with Maggie at the apartment, where Doug is often left to fend for himself. His attempts at creating a normal life for her succeed for a while, but Maggie cannot change the way she is. Doug, suspicious and cynical at first, bonds with Baggs, who devotes his free time to the kid and even gets his teeth fixed. But both know that soon Baggs will be reassigned and gone for good.
The Navy's mix-up continues to baffle Baggs until one day a veteran sailor named Forshay not only finds the file, but volunteers to change places with Baggs and ship out under a false name. Baggs and Doug may not have Maggie around any more, but they've got each other.

Of course now I want to see this as a McDanno fic. oh and James Caan is in it! haha

Steve would be John J. Baggs
Danny as Maggie
Grace as Doug

I don't know who I'd pick for Forshay, though. Joe White, Nick Taylor or Freddie Hart

Also, I don't know that I'd have Danny as a prostitute. Maybe have him undercover as one, though.