grandboomer
n. A grandparent who is a member of the baby boom generation.
Etymology
Examples
2002
Given the "boom" in baby boom, by the year 2006, there will be 80 million grandparents in the U.S. Nearly half of them will be boomers — the youngest, best educated and most active generation of grandparents in history. Already, the average age of first-time grandparents is a spritely [sic] 47. And these "grandboomers" are giving a whole new look to the role.
—Karen von Hahn, “Grandspending,” The Globe and Mail, November 30, 2002
1996 (earliest)
First it was grey hair and bifocals. Now baby boomers are adjusting to another sign of middle age: grandchildren.

But these neophyte grandboomers are bringing a new, informal style to grandparenting. Today's grandmother wears jeans and a T-shirt, wants to be called something other than Grandma (first names are getting the nod), probably works outside the home and is short on time to bake cookies.
—Dorothy Lipovenko, “Boomers' next hurdle: grandchildren,” The Globe and Mail, August 07, 1996
Notes
The leading edge of the baby boom turns 57 this year, so it's not surprising that a good chunk of them are grandparents. In fact, more than a quarter of the cohort — around 20 million of the 78 million boomers in the U.S. — now have grandkids to dote on. Boomers-as-grandparents stories have been around since at least 1996, the year the oldest boomers turned 50 (and the same year the word grandboomer first appeared). As this first wave of boomers approaches 60, expect to see many more such articles and, since these are baby boomers we're talking about, expect most of these stories to talk about how these boomers are revolutionizing grandparenthood (as, so we've been told, they already revolutionized dating, marriage, and parenthood in previous stages of the boomer era).