Emphasize reliability, professionalism, level-headedness and other strengths that come with years of experience.
Do not talk about grand children, being empty nesters, and pensions. You should emphasize that there are no family issues that will interfere with being a reliable worker.
Remember that if a company is going to actively discriminate, you do not want to work there so do some research and find older worker friendly companies. AARP offers a list of companies that are friendly to the 50-plus set, and SimplyHired.com offers a job search feature that lets you search by 50-plus friendly employers.