Is the park well visited by other kids in the neighborhood and does he know the kids there? If not, make some new friends. Or buddy up with at least one. I'm sure if they go there, they go to the same school.
Is the playground surrounded by the woods or something else? Some kids venture into the woods and some don't.

Around 9 would be ok but it depends on how mature your child is and the size of the child. Some 9 year olds come up to my kid's armpit. Same age.

Our playground is about a 5 minute walk. Alot of kids in the neighborhood just go there on their own after school. They've been doing this since the pandemic started. It started with few kids, then it got more crowded now. But, the kids get to know each other from all grades and background. Some of them play for hours. I mean 4 hours!
Some kids are ready for the independence.

If you are not comfortable, just go there a few times with your kid and sit far away to give the child some space to learn to play with others. Get to know some other parents. The kids might not be in the same grade but it's all good. Wear a mask even if others don't.
Maybe bring a ball or something to share with others, if the kid is into balls. My kid hates ball sports so none of that will entice him.

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:I wouldn't recommend alone--maybe with a friend? Probably 10.

So they even care about the park at that age? I don't see 10 year olds at the park.

My 12-year-old son goes to the park! Most of the parks in our area have fields where the kids practice sports on their own, pick up games with their friends, etc. A bunch of nine and 10-year-olds meet up at the school park every day after school.

My 6th grade son and his best friend from school love going to the park together. Every night after he's done his homework he goes to her house, knock on the door and asks if she wants to go to the park with him. They still enjoy climbing up ladders and going down the slide, pushing each other on the swings, playing tag and hide and seek, giving each other piggyback rides, jumping in puddles and playing in the mud.

This is wonderful.
My son also had a girl BFF he used to hang out with at the park, but now in 6th grade she has lost interest.
It sounds like your son has a wonderful friendship.

My 4th grade son does this with his girl BFF the same age (though she doesn't go to school with him)
They go to the park and play together for hours doing a lot of the same things PP mentioned and on Fridays this is followed by their sleepovers alternating between ours and Larla's house.
I wouldn't be surprised if this continues into 6th grade and even beyond that.

Anonymous wrote:

Anonymous wrote:I wouldn't recommend alone--maybe with a friend? Probably 10.

So they even care about the park at that age? I don't see 10 year olds at the park.

My kid and his friends do. They don't care about the playground, but the field is good for just messing around, digging in the dirt, climbing on rocks...