No one knows a son’s swing like his father. And if Ike Davis ever needed help, it is now. So when Ron Davis’ desperately slumping son comes to Arizona next week with the Mets’ Class AAA affiliate, the Las Vegas 51s, he will be there to throw him batting practice. He understands all too well what it’s like to play in the white-hot glare of New York, having pitched for the Yankees. And he knows what it’s like to struggle, owning a piece of the major-league record for most blown saves in a season. “He asked me to come down and throw some BP to him [before the game in Tucson],” Ron said in a phone interview from his home in Scottsdale, Ariz. “So I’m going to come down. We’re working on some things that 26 years of watching will help.” Ron’s wife, Kendall, flew to Las Vegas on Tuesday to watch Ike make his debut with the 51s against Tacoma. The first baseman batted cleanup. Ron doesn’t just know Ike’s swing. He knows it “better than anybody.” And he is sure his son will work his way out of his season-long slump. Father’s Day is Sunday. But two days later will be all about a dad helping his son.