Keep left toys in clearly visible boxes at the playground.
Often toys are still lying in the sand in the evening. These could be stored in old wine boxes. If you are looking for your own, it is easier to find it and if you don’t need it, everyone who doesn’t have anything can help themselves.
In terms of price this would not be a big effort and the workers would have hardly any effort. You could attach the boxes to the fence with cable ties and attach a hibiscus explanatory panel to it.