Demolition: Anything to consider regarding new construction?

Accordingly, there should be no pools and garden ponds.

Children should know that they are not allowed on other people's property and that a fence is not meant to be climbed before being let go alone.

Accordingly, there should be no pools or garden ponds.

Children should know that they have no business on other people’s property and that a fence is not for climbing before letting them go alone.

Pools and garden ponds are rarely located on uninhabited properties. And if you have children yourself, you secure pools and ponds accordingly or supervise the kids. And still, tragic accidents keep happening precisely there.
And forbidden things are especially appealing to kids.
But everyone has to decide for themselves whether they want to take responsibility for that.

Yes, ideally the famous "Parents are liable for their children" sign, which is legally pretty useless. Even if it is legally defensible, can you live with children being harmed anyway?

Oh dear. We better cancel the whole project or the children should not leave their houses until we move in. You do know what a construction site looks like later, right? Do you think a shell building over several months is safer? 500 meters away is a fire pond with a waist-high fence around it, diagonally opposite is an old vineyard house at the edge of the field, next to it is a combine harvester freely accessible all year round. 500 meters in the other direction is a federal road and in between a creek. So far, everyone has survived and I don’t think our hole with a 2-meter-high construction fence in front of it changes that. We are also not building in an open field but in the middle of an established residential area, i.e. to the left, right, behind and opposite are numerous people among whom no children have fallen into the ponds so far. So we will keep our concern manageable.

Even in an occupied house, the pond/pool is often not supervised and stranger children can get in. Which child is deterred by a folded-up pool ladder? Secure the construction site and done. The filling work was only carried out by the house construction company for us. House connections still need to be installed.