Hi Regina,
How are you? Well, let's see. Personally, I check all of the above. Merriam-Webster defines "reunion" as an act of reuniting or a reuniting of persons after separation. Whether it's a large scale, planned events with all the "trimmings" or just a get-together of 15 family members at Momma'Nem's house, it is the act of reuniting, making it a family reunion in my book.

Just my 2 lil cents,
Mel