“Between Me and You,” Ja Rule is about to be a fire grandfather … the 49-year-old rapper tells us he’s already planning for his future grandkid to be “Livin’ It Up.”

We caught up with the Grammy-nominated artist Thursday in New York City after his grandpa announcement … where he told TMZ, “I’m going to open him up a very special account that grows interest over 18 years, so that he has lots of money.”

He was absolutely beaming while signing autographs for fans outside of Sherri Shepherd‘s daytime show “Sherri” — and with good reason.

The baby news comes on the heels of walking his daughter, Brittney Atkins, down the aisle in May, and launching his massively successful premium honey botanical whiskey, Amber & Opal, last year.

Friday, he’ll make his judging debut at the New York Wine & Food Festival’s legendary “Burger Bash,” where he’ll officially announce his Amber & Opal Bar Takeover Tour — a nationwide celebration of music, food, and connection.