If Leonard McCoy had to describe himself "kid person" would not be one of the descriptors. Even when he was a kid, he'd generally been overly serious for his age. (This was due to a combination of the death of his cousin during what should have been simple play time and the subsequent move of his family away from the kids he knew.)
That said, there was a certain kind of patience Leonard found within himself when dealing with the injuries of children. It helped that they generally didn't know better and often it wasn't really their fault. Not that he wouldn't tell them what was what if there was serious danger being had but still. No hypo stabs for the under sixteen crowd.
Still, when McCoy saw the tiny patient seated on the biobed in his Sickbay, a very small part of him wanted to flee to his office and leave her care to M'Benga or whoever else was about. But no. Leonard McCoy didn't shirk his responsibilities. Besides, the tiny thing was wearing wings of some kind, for Pete's sake! It wasn't going to bite him.
That decided, he squared his shoulders and crossed to the little girl. "Hello, darlin'," Leonard greeted, bending down so he was of a less imposing height. "Seems you've got a scrape here needs healin'." The rest of her stats checked out and, honestly, she didn't even seem too worried about the minor injury she'd picked up. Thankfully. Crying adults were bad enough but children? No thanks.
Leonard picked up the dermal regenerator and showed it to her. "I'm just gonna run this over your arm a few times an' it'll be all better. This won't hurt a bit but, if ya like, I can ask Nurse Christine over there--" he pointed to his blonde head nurse, "t'hold your hand." It seemed the thing to offer since he didn't see a parent around.
(And that thought would've earned a frown if not for the child present; he'd give whoever was in charge of this little one a talking to later. Although, intellectually, he knew they were busy moving things and making sure everything was safe but still. This kid was practically a baby!)