Cuba Gooding Sr. -- Allegedly Stole Thousands ... Played Charity For The Fool

Cuba Gooding Jr.'s dad put Scrooge and the Grinch to shame by bailing on a Christmas charity concert for a children's hospital, while making off with a bunch of cash ... according to a lawsuit.

Reginald Lewis says he's been trying to track down '70s soul singer Cuba Gooding Sr. ever since he cancelled a benefit gig for the Kennedy Krieger Institute last December in Baltimore. Lewis claims he loaned Gooding $7,000 to promote the event ... and never got the money back.

Lewis is suing for the dough, but says he can't locate Gooding -- whose group The Main Ingredient sang the '72 hit "Everybody Plays the Fool" -- to serve him with papers.

We reached out to one of his reps -- but same result ... radio silence.