My mother and her sisters and brother planned an early birthday party for my Grandmother's 80th birthday. Her birthday was actually in November, but they had the party in August to make it easier for travellers. My grandmother was totally against it at first, didn't want the fuss, but by the time the party arrived she was involved in planning. Then they did the same thing for her 90th birthday.
And in the strangest coincidence she received 90 birthday cards, the last one arriving a couple of weeks after her birthday.
Another suggestion, if your father-in-law enjoys sports or music or theatre, a concert or sporting event or show together with a dinner makes a special night out.