Starting Strength is perfect for any age. We have a video someplace here showing a 91 year old woman in Starting Strength. There are many ways to adapt the program. Box Squats with a broom handle may be one place. If he is more flexible try a 15 lb empty bar for a starter. If more flexible then you may find a 45 lb. bar will work. Use Technical places (5 lbs each) for deadlift. I.e, he could start with 55 lbs. Tell us more about your Dad and any physical limitations he may have. The best way to start for any of us is to go to a Certified Starting Strength Coach. It is the safest and most effective way to go. BTW how far are you into SS training?