The 3 keys are food, water, and shelter. Do some research (google.com) on habitat requirements for the different species you're interested in and there should be tons of information available. Also, you might check with your local extension office to see if they have any publications on backyard habitats.

There is a wildlife forum here that should be an excellent source of information, also. Check it out.

Just be careful to educate your children about the hazards of wildlife. They are not pets and shouldn't be treated as such. They can be a great source of enjoyment and education but also can be dangerous if not treated with respect. (Cautions you probably didn't need but... ;-)

Sandy