I've been lucky to teach many students whose families were extremely charitable and they built that wonderful trait into their daily lives. While writing checks to a charity is certainly admirable and important, it is not as strong an example for your kids as actually doing something to help others.
One family had a tradition on their birthdays. After opening their birthday gifts, the child (or parent, depending on whose birthday it was,) would choose one gift to donate to charity. They would then travel together to physically give that gift away. It was a wonderful demonstration of the importance of helping others who are less fortunate.
Another family worked together one night each week to cook meals for a charity. They had a great time cooking by side by side, along with other families who shared their vision. Sometimes they would volunteer to bring the food to the home or actually serve the guests they had cooked for.
Since my kids were little, we have done many things to help others. Our favorite occurs every Thanksgiving when we create 40 traditional Thanksgiving meals, filled with turkey, cranberry sauce, veggies....all the fixings! A juice box, napkin, plastic ware and brownie complete the meals. We then drive to the boardwalk in Atlantic City and hand the meals out to the homeless.
It is my family's favorite day of the year, and now we've been doing this for so many years that we would all be heartbroken if the tradition ended. Watching my kids help a homeless person stick a straw into a juicebox is truly an overwhelming feeling. What could be a more basic way to help someone? When my older kids applied to college, they wrote about this experience. Their words were personal, and extremely meaningful. They truly understand what it means to give back to others.
Choose something meaningful to your family, and get your kids involved. We started off when the kids were very small by playing bingo with residents of a nursing home. There are plenty of things little kids can do, and the lessons are invaluable.