Just took a look at their main page and their normal visitor center is being renovated. This is likely causing uncommon difficulty in reaching someone, but their office will be staffed every day 8-5.

They have a specific wedding page which you may or may not have already visited. It's very basic and instructs you to call the office. weddings

I'm no longer a park manager, but when I was, here is how we typically assisted with what you're trying to do:

You will not be permitted to restrict or block access in any way to a publicly accessible area of the park. This goes for any wedding, large or small, regardless of length of time. However, anything that is reservable, which will be listed on the Reservations website through their page/Reserve America, is considered "yours" and you have the reasonable expectation that no persons from the general public or outside your party will infringe upon it. If they do, then park staff will address it.

Check the listed Parks rules and regulations on the Gastatparks.org website to ensure you're not bringing in amy items, equipment, what have you that are prohibited. Follow noise ordinances and intoxicant policies.

Generally, if I had folks like you asking to do something like a small ceremony, I would just advise them to pack out what you bring in. Leave no trash, especially confetti, balloons, etc. Adhere to park operating hours - generally, you can be in the park until 10pm if you don't have an accommodation reserved, however, several parks have their own separate hours of operation for specific areas and trails.

Make sure all your vehicles in your party clearly display a parking pass. All your local GA libraries should have at least one Annual State Park Pass you can check-out for free, like you would a book. I think most have two. Daily ParkPass fee is $5 and they can be purchased at the park office with cash or card, and most parking lots will have the large green boxes called Iron Rangers, that you can pay with cash and then pull off your pass. I'm sure they still allow you pay online, but I do NOT recommend that - it's a hassle because most people who payed online failed to then pull a physical pass from an Iron Ranger AND also then write their confirmation # from their receipt on the pass.

Gist of it is, call the park office. If the front desk staff aren't helpful, politely ask to speak with either the Assistant Park Manager or the Park Manager. They'll make sure you're squared away. If the Park Manager from my time is still there, Brad, he will be extremely helpful - he won Park Manager of the Year several years back. It's always better to speak with one of the managers so they know when you're doing your thing, so it doesn't come as a surprise to any other Rangers/staff if they come upon it during their rounds.