First of all make sure you can have an open discussion with you child about people that are less fortunate. It is important that children know the difference between being able to afford the grocery staore or using a food bank to survive. Children will understand and want to help when they know why. We often clean out the closets and drawers and stuffed animal pile and as we do so each child knows that what goes into the give away box is going to be shared with some else who is ready to love the toy or clothing. We often go into our local thrift shops and see our belongings that we have given away being purchased by someone else. My children see the smiles and joy on the faces of other children and that makes them happy to have been able to give that gift.
As for the people that are ill, infirm you would need to talk to some of your local hospitals they will have a volunteer program you and your children can join and visit. As for the disater area there are many stories on the internet about how young people have put together packages that contain simple things such as soap, pencils, paper and simple toy that can be distributed through Red Cross.
The ways are endless, although it all take supervision and organization. Good luck. :)