The biggest trick will be convincing them to start saving & investing now, reducing their spending now, so they do not have to reduce income catastrophically when they retire. It sounds like they will carry the mortgage into retirement. Maybe they should downsize now. They should probably start saving 30% of income, but that will be a major hit to their current spending. Could you make that kind of adjustment yourself? Just something to think about.
Are you sure Dad does not have a pension or deferred account, and has just forgotten about it? Essentially no savings and approaching 60 is kind of tough.
They have 8-10 years to save. Whatever they can save will be better than nothing. Hopefully, they can be convinced. Some people cannot make the change. They would rather keep their current lifestyle and worry about the train wreck when it happens. You are their kid, and it is hard to take advice from your kid. I ran into that problem with my parents. You may have better success if you go with them to a financial counselor.