Ballpark mysteries. Main series

Batting second—and perfect for Halloween—book #2 in an early chapter book mystery series where each book is set in a different American ballpark!
Mike and Kate are waiting for Kate's mom at a boring press conference in Yankee Stadium when the team official says something that makes Mike perk up his ears. There are rumors that the ghost of Babe Ruth is haunting the new stadium! A chill air blasts down a service hallway...

Now batting clean-up—book #4 in a new early chapter book mystery series where each book is set in a different American ballpark!
Houston, we have a problem! Before a game at the Astros' ballpark, Mike and Kate get to meet astronaut commander Nick Rice at the nearby Houston Space Center. He's planning to display a very rare moonrock at an autographing event later. But just before the event, a nefarious outlaw knocks out the commander and...

Next up to the plate—book #6 in our early chapter book mystery series, where each book is set in a different American ballpark! 
Ivy-covered walls—they're the most famous part of the Chicago Cubs' historic ballpark, Wrigley Field. Mike and Kate can't wait to get down on the field to see the ivy for themselves. But when they do, they're horrified to discover patches of the ivy have been ripped away! Who would want to sabotage the...

It's the eighth inning! The Missing Marlin is book #8 in our early chapter book mystery series, where each book is set in a different American ballpark!
Mike and Kate are in Miami visiting Kate's Uncle Oliver—and the Miami Marlins ballpark, of course! Uncle Oliver is in charge of keeping the new fish tanks at the ballpark fully stocked, but strange things keep happening. Kate swears she saw an endangered sea turtle in one of the tanks....