You are going in with a very good attitude. I'm sure you'll do fine. Just one note. It's much easier for a quiet band to sound good at that level than for a loud band to drop their volume and sound good. (That was so clumsy, I'll try to say it again.) Bands that usually play at low volumes and sound good, can change volumes and still sound good. Bands that are usually loud and sound good, have a hellish time turning down and still sounding good. (Better to start low and get louder than to start loud and attempt to get lower.) It sounds like I'm just stumbling over my own words. Oh well. Knock them dead. (And don't forget to have some fun while doing it.)
Stumbling over your words or not you are still correct. In other words: it's easy to turn up, but harder to turn down.
I tell every drummer I work with, that uses an acoustic kit, that I need to be able to rehearse with them with no amp or mic. Just me and an acoustic. If I can do that then they are in. I love it when bar owners/managers complain that a band was too loud. I tell them it's usually because of a loud drummer. Loud drummers=loud bands. The majority of them are beaters. And of course bands turn up around the loudest source. I hate loud drummers. I play a several outdoor venues with noise restrictions. I went to one once after leaving something there. Had to pick it up the next night. The band was playing and all I could here was drums. I asked what the heck was going on. I was told that the band was too loud and they asked them to turn down. So they did. All you heard now was the stage noise. That noise would be the drummer. Now the band was playing but almost nothing was in the mains and they still asked them to turn down. Bar staff doesn't understand that stuff.
And a lot of times guitar players too get whiney. Whah, I can't hear myself. I had one of those two weeks ago. Kept trying to turn up his amp. It was a Mesa combo and he was standing over it. It was hitting his calves. So all I did was lean back the cabinet. Wow, that took a genius to figure out.
One time I had a bar owner actually tell me he was going to ask a solo act to not plug in his guitar because it was too loud. He thought he would just play his acoustic unplugged and vocals mic'd. Huh? I pointed out to the owner how bad that would sound, and not work. I had to explain that it's a solo act and nothing is coming from the stage, and he needs to tell the guy to turn down the volume. It was a total duh moment.
Point is Wynnd is correct that it's easier to turn up then down. I spent 6 years with a guy who played an electric kit at a lot of our venues. We had a lot of happy bar owners. And on a rare, yes rare, occasion we were actually asked to turn up. That's unheard of! Lol. The good thing about my drummer was that he knew how to play the acoustic kit quietly too. But at a small venue even some of the most quiet drummers are still too much.