If David Cassidy, of ³The Partridge Family² fame and former headliner in the MGM's ³EFX² show, chooses the All-American SportPark, 121 E. Sunset Road, as best family attraction in Las Vegas. Cassidy, his wife, Sue, and their 8-year-old son enjoy the variety of activities at the new park everything from batting cages, to miniature race cars, to a rock-climbing wall. A close second with Cassidy is the dolphin exhibit at The Mirage, 3400 Las Vegas Blvd. South, where children can see the animals up close, and adults can sit back and enjoy the soothing tropiclike surroundings.