Okidoki!
Great idea, go for it, as others have said!
Now, to opera!
It's the 17th c. (or the 18th), check. Opera at this stage is ITALIAN opera. BUT what people wear and what kind of crowd you get depends on where the opera is staged.
Opera is an art for kings, so a lot of opera is concentrated in the opera houses built for the courts - French court, Austrian court etc.
Forget about tuxedos, tails etc. as formal wear. They're all 19th c. fashion. The courtly and/or uppercrust audience woul wear their best clothes according to the fashion of the day in general. If it's Italian opera in western or central Europe, they will look like the Paris fashion. I.e. something like this:
The image is a shot from the French historical movie about Louis XIV "Le roi danse" (the king dances), which is very much a film about 18th c. French monarchical power and opera, of course.
It certainly was a pretty weird environment and the movie is visually stunning, so by all means check it out if looking for inspiration about the look and feel of 18th c. opera.
There would be socially mixed opera audiences as well, particularly in Italy where opera was a popular (as in folksy) art form. The less affluent part of the opera audience would wera no special clothes and be up in the cheap standing-only seats in the section up under the roof of the opera house known as "the Gods".
I guess you must already have thought about snooping about for literature about opera house architecture.
Otherwise this is a nice 18th c. opera house still maintained in historical condition in Sweden, built right by the summer residence of the kings of Sweden, and their court, in the 19th c., "The Drottningholm Opera House". King Gustaf III of Sweden himself might have strutted his stuff on stage, just like Louis XIV of France a century before him would dance the ballet literally as the Sun King: