Start from the position of the 85-year-old gentleman. Your father is his first cousin (because they share common grandparents). Further, any child of your father (or, indeed, his grandchild or great-grandchild) is also his first cousin (because the link is via through his grandparents). However they are 'removed' by one (or more) generation(s).
So you are that elderly gentleman's first cousin, once removed (and vice versa). If you've got children, they're his first cousins, twice removed.
Chris
(PS: To be second cousins with someone you need to have great-grandparents in common)