The Great Outdoors (1988)

Big-hearted Chicago family man Chet has brought his family to a lakeside resort area, and although his wife and kids aren't quite as excited as he is, Chet has high hopes for the vacation. However, his optimism is sabotaged when his obnoxious brother-in-law Roman drops in unexpectedly, along with his snooty, strange family. Chet and his family try to stay open-minded, but they find it difficult to relax and enjoy themselves because of the constant annoyance of Roman's presence.