Every garden bird has its own way of building its nest, so each of them need different type of house. You may buy these houses or you can build them your own, it is not too difficult and may be a weekend project with your children. The simple the better. Use leftover materials that you have in your garden or shed and try to be as natural as possible.
Colorful and fancy houses may not be as attractive for them as a simple and natural home that will resemble with the one that they will find in the nature. Few pieces of wood and the house is ready. You can decorate it with sticks or make a green roof using some succulents or ground cover plants if you feed the need to make it more decorative, but just make sure you keep it as natural as possible. Place the houses in sheltered places, away from cats or other predators. Make sure you hang them safely.
You can even hang somewhere in your garden a box with pieces of strings, small pieces of fabrics, wool or any other materials that they may use to build their nests. Also keep providing them food and fresh water and regularly clean them as dirty water and food may get them sick.