I will travelling to my nearest Apple Store in the UK this morning. I am torn between the 13” and 11” iPad Pro. If this helps, I will be 56 this year. I have no problems with the 11” for general use. I even have my iPad set to use “more space” which makes everything smaller. That said, my eyes are not typical for my age as I do not need glasses for anything apart from very small text in low light. However, if you do wear glasses, I would imagine the 11” would be perfect for your needs.
I have reservations about the 13” iPad, which is why I am travelling 50 miles to see it in person. At the moment, I am typing this in bed, with the 11” iPad held comfortably aloft in my left hand and typing with the right. I need to be able to do this with the 13” or it’s a bust. I have held the 12.9” iPads before but I always found them too heavy and cumbersome. I’m curious to see if the much thinner/lighter 13 iPad changes the equation.