Worm, I could be wrong, but I think if your other trees were in danger that they would already have it. Ayers and Moonglow are the most resistant pears I have ever seen, and I would be surprised to see them infected. I also suspect that your Kieffers are not true Kieffers, because even though they can get FB, I've never seen it that bad. I have several trees bought as Kieffers that are close but not the Real McCoy....
Your situation is a tough call. I will tell you one story that might interest you - My neighbor had an apple tree that was infected so badly with FB that I thought it was going to die. I had never seen anything like it. It set 30 yards from one of my Ayers, but my pear was not infected. He didn't do anything to the apple tree and somehow it lived. Three years has gone by and his apple tree has grown new limbs and you can't tell it was ever infected. This year it is loaded with fruit.
His apple is a full sized Milam tree on its own roots that was dug up and transplanted. It was 12 years old, and when it got FB was the first year it flowered. I think this just reinforces the opinion I have had for quite some time about the advantages of large trees on their own roots. If that had been a dwarf or semi dwarf, I think it would have died. I'm going to predict that in the future that his tree will see some more FB but it will always be able to survive it and probably will be a good fruit tree for him.