If other parents expect planned meetups, then "organically" is exactly that. Even if they take no issue random meets in principle, they already planned most time for other things. Their kids are not outside to be randomly met. Often other kids don't even live within walkable distance.
For that matter 3-6 years old don't "organically" start to visit each other alone without parents. How exactly you expect that to happen, really?
If other parents expect planned meetups, then "organically" is exactly that. Even if they take no issue random meets in principle, they already planned most time for other things. Their kids are not outside to be randomly met. Often other kids don't even live within walkable distance.
For that matter 3-6 years old don't "organically" start to visit each other alone without parents. How exactly you expect that to happen, really?