Thanks to both of you.

I'd poked around a bit on Google, but was a bit skeptical of the results I was getting - companies offering limo/bus service for hundreds of cities, for example. Adding "Reisebüro" to the search totally helped. We might also reach out to the hotel, although that would require us actually agreeing on a hotel, etc.. Unfortunately, while there is a group of us going, there's no actual organization, we're all kind of on our own for booking everything.

We're also a bit constrained by luggage: we're going to a fencing tournament, so every kid will have roughly the equivalent of a golf bag in addition to regular luggage. At least we're only there for a couple of days so we don't need that much in the way of clothing.