Control the space before any greeting happens
In a shared park, safety starts with distance and a short lead. Keep your dog on lead near play areas, paths, picnics and sports games, even if he is allowed off lead on the open field, and step off the path to let excited children pass rather than letting them flow around a dog who cannot move away. Stand between your dog and an approaching group, which gives you a polite barrier and gives him a person to hide behind. Watch the whole picture, not just the nearest child: a football rolling toward him, a toddler running with a stick, or a scooter coming from behind can startle a dog who was coping perfectly well with the child in front of him. If the park is filling up and his body is getting tense, leave early rather than squeezing in one more lap.
Run every greeting the same calm way
When a child wants to say hello, go through the child's adult first, and be cheerfully willing to say not today if your dog is tired, hot, eating a chew, or already turning away. For a greeting that does go ahead, keep it brief: dog standing or sitting sideways to the child, lead loose but short, one child at a time, a low hand offered to sniff, then a stroke on the chest or shoulder rather than a pat reaching over his head. End it while it is still going well, call your dog back to you, and reward him for leaving. Teach regular young visitors in your life never to hug him, chase him, pull ears or tail, or follow him when he walks away, because a dog whose retreat is respected rarely feels the need to escalate.
Read your dog, not the children's intentions
Children mean well and still overwhelm dogs, so your job is translation. A wagging tail alone does not mean a happy dog: look for a loose, wiggly body, soft eyes and a dog who chooses to move closer. Step in and create distance if you see lip licking, yawning away from the child, ears pinned, a tucked or stiffly flagging tail, freezing over a toy, or the whites of his eyes showing as he tracks a running child. Never punish a growl at the park. A growl is early, useful information that he has had enough, and the safe response is a calm exit and more space next time, not a telling-off that removes his warning while leaving his worry untouched.
Practise park manners away from the busiest hour
Calm behaviour around children is a trained skill, not a personality test your dog passes or fails on a Saturday afternoon. Build it in quiet sessions: walk past a playground at a distance where he can notice children and still take treats, reward settled watching of bikes and running games, and practise recall away from a friendly helper before you ever rely on it near a play area. Keep sessions short, finish while he is succeeding, and be honest about the venues that suit him, since a dog who relaxes on a wide field edge may never enjoy the narrow path beside the swings. Noting each practice session, what distance worked and what tipped him over threshold in KinsLe Care Teams lets anyone who walks him build on the same training instead of starting cold.