All wedding guests get a day pass into the park; just mention the wedding by name at the gate into Sylvan lake. However, if you plan to make a weekend of it, you will need a pass for the other days.
There is a decent amount of parking around the lake. They will also provide a shuttle down from the lodge if you prefer to park at the lodge. I am unsure about the details on how long that shuttle runs, but I will update this page when I have more info on that.
We personally are staying through Sunday morning. Anyone who wants to hike Black Elk Peak (formerly Harney Peak) with us Saturday morning is welcome. There are so many things to do in the park or neighboring areas, so we highly recommend making it a vacation if you can. I put a few recommendations in the "Things to Do" page, but if you want more specific recommendations for experiences or meals or places to take kids, please reach out. We love the black hills and would love to share some ideas with you.
Mountain Time. I will try to list both on the invites and information, but when in doubt, assume it is mountain time, especially for events in Custer.