I listened to the tape last night. Now, it's important to remember that the mixer tape out isn't necessarily what the audience heard.

But that said, the levels were all off, except on the pipes+fiddle sets. The vocals, bodhran, and cittern were way too high. The gain on some of the vocals was probably too high too, meaning distortion. The fiddles and guitars were too low; although if the cittern and bodhran came down, that might have no longer been an issue.

UPDATE:
The above is all kinda moot - apparently the sound wasn't recording from the mixer. I forgot to set the source to "line in". It was recording from the laptop's microphone! Oops! No wonder it sounded so bad. And that I could hear Andy real well when there was no mic anywhere near him (other than the laptop's). But the lessons learned are the same.
END UPDATE

The pipes+fiddle sets were almost just right. A bit more fiddle in them would have been nice (or rather, a tad less pipes).

Lessons learned:
1) The sound guy's job is very important. If I'm going to conscript people into the job, I need to train them (and get trained myself),
2) The sound check needs to be much more than "how do we sound in the monitors" (and even there we need to do it all instruments blazing),
3) If possible, the "front of house" mixer should actually be... well... in the front of the house, where the sound guy can hear what the audience hears.

It's always a learning experience.