A 43-year-old Queens man celebrating Independence Day with his wife and 5-year-old son at Playland Amusement Park drowned yesterday after wading into a restricted lake from a crowded picnic area. Won Yong Kim of Flushing was pronounced dead at Greenwich Hospital at 1:25 p.m., a little more than an hour after other patrons of the crowded county park noticed him in distress off Playland Lake's shore. His wife and son were in another part of the park at the time.