Because he feels that the conversation he has had and using Scrooges name in their game has brought them "much merriment"
He felt for his old uncle and as this was his only relative he wanted to wish him health at that time of year
He wants to make a toast to Scrooge
Fred States "Here is a glass of mulled wine ready to our hand at the moment; and I say, 'Uncle Scrooge!' " "Well! Uncle Scrooge!" they cried. "A Merry Christmas and a Happy New Year to the old man, whatever he is!" said Scrooge's nephew. "He wouldn't take it from me, but may he have it, nevertheless. Uncle Scrooge!"
Scrooge's only living family member was his nephew, Fred. Fred was the son of Scrooge's sister, Fan.
Scrooge's nephew's name was Fred. He was a kind and jovial character who always tried to bring cheer and goodwill to his uncle, despite Scrooge's grumpy demeanor.
Fan was Fred's mother but died giving birth to him and Ebenezer Scrooge never forgave Fred for it. Just like Ebenezer's mother died giving birth to him, and just like Scrooge never forgave Fred for 'killing' Fan, his father never forgave Scrooge either.
Fred, Scrooge's nephew
she died when she gave birth to Fred, Scrooge's nephew
Simply to invite his old uncle to dine with him and his family
Fred is the son of Scrooge's sister. He is Scrooge's nephew and he refers to him as Uncle.
Fred, Scrooge's nephew, stops by to invite him to a Christmas dinner. Despite Scrooge's initial reluctance, Fred continues to extend the invitation out of goodwill and to mend their strained relationship.
Fred is the only son of Scrooge's sister Fran, and his only living relative. Fred makes it clear in "A Christmas Carol" that he wants nothing of his uncle, except for his acceptance of an invitation to dinner. Fred knows that Scrooge is his own worst enemy and renews the invitation every year at Christmas. One of Scrooge's greatest acts of contrition and redemption is to finally accept his nephew's invitation, and make peace with Fred's wife.