I agree with pp’s it doesn’t look like an XL bully, we have a few around here and they are very distinctive with massive heads, gorgeous but scary dogs.
It looks like the dog I had growing up which was a staffy mix, she was the sweetest thing who wouldn’t hurt a fly and was scared of her own shadow but people were always scared of her because of how she looked which I totally understand.
I think OP is getting a hard time, I am a huge dog lover but when my DC are with me I do get more nervous when I see a dog running around off lead, especially when they were very little like OP’s DC.
The dog sounds absolutely fine and was causing no trouble but it is never a good idea to have any dog off lead near a children’s playpark and I cannot believe how many people seem to think that it is.