There are no major hotel chains near the track. There are some toward Atlantic City but that's far away from the track.
You guys can call this hotel. It's close to the track and what we usually use. When we were there two weeks ago, I tried to set up a block of rooms but I only have about 15 people committed to the track and they laughed at me trying to get a group rate for ~10 rooms. For the record, I doubt people will register strictly based on the fact that a hotel is chosen.
Their rate is pretty cheap to begin with so not getting a group rate shouldn't be that huge of a deal.
Millville Hotels near Wheaton Arts Center: Country Inn: Hotels in Millville, New Jersey