The former NY Giants head coach -- who led the G-Men to two Super Bowl titles -- also runs the Tom Coughlin Jay Fund Foundation, which raises money for family's affected by pediatric cancer.

Coughlin named the charity after one of his former players, Jay McGillis, who played for Coughlin at Boston College.

McGillis was diagnosed with Leukemia in 1991, during Tom's first year as head coach. He passed away 8 months later.

Enter Manning, who says Tom's charity is one of the things he's most passionate about in life -- and he's calling on some of his rich teammates to help the cause.

"A great way to celebrate his birthday, the best gift we can give [Coughlin] is bringing attention to the great work he’s been doing for the last 25 years in helping families that are struggling as they deal with a child that has cancer," Manning said.

"So, it's a little challenge to everyone that played on Super Bowl 42 and 46 [or] if you played for Coach Coughlin at any point, let's come together and help the Jay Fund and raise some money."

Obviously, there are some super-rich guys in that group ... from Michael Strahan to Justin Tuck, Amani Toomer -- and Tiki Barber.

No pressure ... but here's hoping they all accept the challenge!