Wow! The approaches are confusing and I have barely started. Rikki and John,you both have valid points. If Hannon is useful for finger strengthening and arps,that is fine,but if I use a keyboard,it is not like the hard feel of a Steinway. Arps,however,are important. This ties into what Rikki said about how much time to spend on what at age 79. John,your later approach make sense to me.

I can do the following:
1.Read both clefs
2.Know inversions of most common chords on both hands.

Have trouble with independent timing of left and right hand.

I have an easier time playing from a lead sheet,but the left hand is inferior to the written part would be in many cases. The right hand borrows notes from the left and the voicing of the chord is not a matter of chance, I do know that it is recommended to use the nearest inversion in a LH chord change,many times the root is needed. A written part will tell you.

Maybe a little of both until I find my way.