Stay

We have a couple of hotel blocks (listed below) within walking distance from each other in Gonzales, Louisiana. The hotels are right off of I-10, exit 177, coming from either the New Orleans or Baton Rouge airport. It takes about 15 minutes from the hotels to get to the wedding.
Sydney and Austin are staying at the Springhill Suites by Marriott.
For group stay, there are some AirBnB and Vrbo homes in Prairieville, Gonzales and Shenandoah (Baton Rouge). They are limited in number, but very reasonable in price.