Baby Birds Dead

Hi all, hope you can help.. we have come outside today after having a nest above our side door for a year or so, this nest was directly under the pitched part of our roof and it seems the wind has blown it down.

We now have 3 dead chicks on our drive :( will mummy come for them? What should we do?

For future, is there anything we could have done better to protect this nest? We’d obviously not have been able to get to it at the height, but just wondering if anyone else has prevented this problem ? Would a nest box in the garden (Maybe on top of garage so no cats) encourage nesting elsewhere?