Alakaline foods are raw fruits eaten properly. Otherwise most foods that are chewed to a liquid prior to swallowing will also me alkaline, "IF" all the foods prior were also chewed to a liquid.
If you have looked around, the one thing I made for all older folks (and those wanting to stay young) is the Longevty Spices. Please read the web site and you can see many ideas I have for longevity. BUT "IF" your dad has little interest, you can at least learn for yourself.