Going to Mustang Island for a wedding in September. While there, I plan on bringing a few rods. I have decent saltwater fishing experience, however I have never fished here. I was wondering if there are any good spots or am I better off getting a charter. Any rod/reel combos? Should I bring a heavy rod in hopes of catching a monster red? What species should I target? Looking forward to hearing what you all have to say!

Mustang island is pretty large, from Port Aransas on the north side to Packery Channel on the south.
Starting at Port Aransas you have the jetties which are very popular for many species and numerous guides and party boats operating out of the port. Hwy 361 runs north-south giving access to the beaches and the bay down to the Packery Channel which has some very nice jetties that are paved.

Go on YouTube and look up packery channel, Port Aransas jetties, mustang island state park and you will find a bunch of videos that show just about every place to fish and how people are doing things. Really a great area.

If you're gonna be close to Port A, they're a lot of good places to go kayak fishing too like the Lighthouse lakes or Shamrocks Island. Lemme know the details, and I'm happy to give some pointers.

Your best results, other than a guide trip, should be at the jetty in Port A.
September the anchovies will be schooled up to spawn and if they get stacked up against the south jetty it's game on.
It's also the time of year when the big redfish stack up in the channel to spawn.
Have a good trip!