As they take a break from next weekend's Mermaid Parade preparations, they will be urging the City Planning Commission to fix their flawed plan that has shrunken Coney Island itself. What Coney Island is, is a place for amusements. And since the city's plan, which started out with a larger acreage for amusements, have diminished it down to a kiddie 9 acres. The plan which had ample approval had since been faced with huge controversy. The city has completely ignored the voices and pleas from amusement advocates at the steps of City Hall last week.