Do you rent out a locker and bring your own towel? I called the park and the woman on the phone seemed like it was her first day! Anyhoo, thanks in advance.
There are several areas around the Boardwalk section where you may rent a locker to store your belongings. Again, getting there early in the day will ensure that you are able to get one easily and not have to hunt around for one when it becomes crowded.
As far as towels I am not certain, as when I went, my group and I rented one of the cabanas and the package we chose included towels with the deal. If you bring one and decide to leave the boardwalk area just throw it in your locker, the Boardwalk closes at 8pm so you should have enough time to get back there later on. The whole park closes at 10pm.
One last thing, not sure what time you are actually getting there Wednesday night, but Hershey will allow you into the park the night before starting at 7:30pm for a preview of the park for free, just be sure to present your tickets when you go. If you have purchased your tickets ahead of time this is a great way to enjoy a few extra hours at Hershey, walk around the park and maybe plan your attack for the next couple of days, and possibly catch a ride or two, or even better yet, a Hershey hot fudge ice cream sunday :)