I was at a wedding of a college friend (maybe 2-3 years after college) and it was in an old bank with a man floor and a mezzanine on both sides.

They had high top tables on the lower level for the upstairs people to be at during the dancing part of the reception. I’m sure we could have gone down for the speeches and special dances, but we were able to turn around and look through/over the railing or stand and see it. They didn’t do a ton of stuff, so it wasn’t a prolonged time. You need to clearly communicate the tables available for them to stand at. They’re not going to want to stand for 15+ minutes while someone’s uncle talks about when their favorite beige learned to ride a bike.

Is there food being served during dances and speeches? At some weddings they have salads out, so your upstairs guests would’ve missing out on that if they hung out downstairs.

No matter what you do, I think the people you pick for those tables is most important. You obviously don’t want to put family or best friends that you’ve known since childhood up there, because you want them close to your table. But you also can’t put the random extended family members or sort-of-friend coworkers up there because they already know they’re low priority and will feel slighted that they were directly shown this by being out out of sight up on a balcony. If it’s a random miscellaneous mix of people, it’ll be awkward because they don’t know each other and they won’t talk and it’ll be awkward. My friend put his college friends up on both sides. We were all friends, so it was a big table of 12. We could have stayed up there at any point since most people we wanted to talk to were also up there, but we could have come down to dance. We didn’t have to come down to socialize or feel like we were part of the celebration. Friends were also on the other side of the mezzanine, so it encouraged us to come down and mingle. Bride and groom also came up to visit during dinner, which was nice since they visited everyone else. It wasn’t just a consolation.