We go to the park almost daily. We go for a nice walk and then usually end up at the park.
The playground at our park is rated for aged 18 months to 12 years and has a staircase as well as various ladders. The little ones have to use the stairs only and the small slide (the one I can stand beside and help as they are learning). The older ones can climb up to the top and the bigger slide. I have a few rules:
-if you can't safely climb off of something, you may not climb up it.
-if you are wearing crocs or flip flops, you may only use the stairs and you may not climb on the ladders/monkey bars/other metal climber things.
-we stay together as a group
-woodchips stay on the ground.
There are probably more that I can't think of right now.
I will add that I have an older group of kids for the most part, so while we play in the yard, I find we also need to be out walking and burning off energy at the park too.
Last summer we hardly ever went to the park. I had some dcks that wouldn't listen to me and I didn't trust that they would follow my direction as well I had a set of siblings who fought and SCREAMED all the time with each other, so I didn't really enjoy dealing with that out in pubic.
I'm sure if you stayed in your yard it would be fine. I don't think you need to say anything to the parents unless they ask. Maybe save park outings for days that some dcks are on holidays and you have lower numbers.