Your canine is allowed off-leash throughout the entire park but must remain in sight and under voice control at all times. The park is not fenced, or at least not in its entirety, so if your canine likes to run off, they certainly could make some good ground. Even if they remained in the park, they could quickly become entirely lost over the large square footage.
The Shawnee Mission Dog Beach does have a pretty strict set of rules and regulations; those can be found on their website. They also require your canine to be registered with the city and provide proof of vaccinations. The lake water may not be the cleanest so be sure to bring your water and water bowl.
There is access to clean water at the entrance to the park, but that is the only location. At that entrance as well as several other places throughout the park they provide doggie bags and trash cans to clean up after your canine. You canine could walk with you along the trails or run along beside you if you wanted to get some exercise in while your canine played.
The trails go through the forest and along the lake but some can be uneven, and others could be quite muddy after recent rainfall. Overall this parks stands out as an incredible place to bring your canine, and it gets the traffic and attention of dog owners all over the state.