Vacation with newborn?

Re

My whole family is going on a mini vacation in late July, potentially early August. Our baby will be anywhere from minimum 3 weeks to a month and a half old when we go(depending on when baby decided to make an entrance). The drive for hubby and I is only about 4 hours so it’s very doable for us to make stops when needed. As of right now the mini vacation will probably be 5 or so days long on the coast of South Carolina. Now I know how hot and humid it gets down there during that time. My question is what should we bring? What should we leave? Have any of you done a mini vacation with a newborn? How would you handle a beach situation? Also we will be in a vacation house so we will be able to do laundry.