[X] Swing by Harry's place to pick up Mouse for a night on the town. We'll take him and Rosie out for ice cream, then just enjoy a few hours of freedom. If that also involves Mouse riding around with his head sticking out of Black Rider's sunroof, then so be it.
[X] Meet with Harry and Mouse for ice cream, or if Harry's not in the mood just with Mouse
Still not a good plan to drop in on strangers with Rosie in tow. It needlessly complicates things and has risks associated with it.
I mean, it's worth noting that Rosie is as low on the totem pole as it gets; in the ocean that is the supernatural world she's somewhere around krill.
We can protect her to a degree, but she's still really vulnerable. Anything that goes wrong will be more complicated and riskier for her involvement.
There's also the potential issues with just being seen as interesting in the wrong place and with the wrong people.
Which we aren't actually guaranteed to catch, similarly to how we didn't know people where watching Dresden's place closely enough to drop a sniper on it with less than a half hour's warning until they took a shot at us.
Not that I expect something dramatic to happen, but there are plenty of potential issues that could come up that aren't.
My general point here is that we should keep in mind that this isn't Harry Potter. The supernatural isn't friendly, or even terribly nice, most of the time and humans aren't the ones running it.
While not quite as bad, for someone like Rosie in the Dresden Files poking the supernatural is a lot closer to 'Warhammer fantasy peasant finds a glowing doodad' than 'muggle sees a house elf'.