Keep the line of communication open regarding health issues. Ask sensitive questions, and listen carefully. They may be embarrassed to tell you about a problem, like blurry vision. If all they need are new glasses, then great, but you don't want them driving until you know for sure. Be ready to offer respectful solutions.
Prevention is always cheaper.
Help the older folks stay stimulated and involved. Studies show that a curious and engaged mind may keep serious dementia at bay for years, and certainly makes life more fun. Keeping active is healthier for everyone. For younger parents, encourage them to develop parallel interests like teaching, consulting or a craft business that might provide part-time income in retirement. Not only is it fun, the extra income can help bridge the gap between Social Security and Retirements funds.