I am 80 and my brother is 86. I haven't seen him for 30 years because we live about 2000 miles apart. I will be near him in a week.

My last visit with my brother I will never forget his looking at me and saying: "I don't know why; I am having a hard time letting you go this time" and I said "It's because now, in age, we are afraid we won't see one another again". And we laughed, shed a tear, and parted. It was the last time.
They happen. Don't try to plan what you will say or what will happen. Allow yourself to celebrate this meeting. Happy memories to you both.

Why are you visiting? Is he dying? Or just you will be in the area? Just give him a hug and say "it was good seeing you". You do not need to say goodbye.

I would try to visit. Perhaps let him know you're in town and would love to see him.

Go out for ice cream together and keep it short and light. If you haven't seen each other for 30 years, I can't imagine that there's any more feeling there except what you might feel for, say, a childhood neighbor.

Depending on the reason you haven't seen each other for 30 years, it might not be worth the emotional upheaval to see him.