x2 on both replies.
Holly Shores is just far enough away from the 'honky tonk' of the Wildwood boardwalk areas. It's a short drive into Wildwood for the amusement piers, arcades and the widest beach around.
Frontier town is a bit more open and on the bay. They have a water park on the grounds and I believe admission is included with camping. The Wild West show is extra, I believe. Again, it's not a bad drive into the 'honky tonk' atmosphere of Ocean City.
IMO Wildwood has a larger boardwalk and more amusements. If you do go to Wildwood, take a ride on the Cape May - Lewes Ferry and watch for the dolphins. You don't have to take the car and just enjoy the 70 minute cruise.
Enjoy wherever you choose.