"extending him" is correct and can be used in written English.
For example, "The manager showed his appreciation for the employee's hard work by extending him an invitation to the company picnic."
"We're in negotiations with Kurt right now, in terms of extending him," Isiah Thomas said.
Nine shots on target exercised Dean Lyness in goal without extending him.
Do join me in extending him a congratulatory (virtual) high-five.
The Knicks picked up the fourth-year option on Toney Douglas, extending him through the 2012-13 seaton, aboutout $2 million.
The accolades and attention received probably outweigh the price that the team and Jackson will pay from extending him for a single game.
They waited to anoint Jerry Reese as general manager after turning Coughlin into a seat filler at the Academy Awards by extending him.
Brandis wrote to Dreyfus to extend him the same offer.
Prandelli is prepared to extend him a fatherly hand, in part because Prandelli needs him.
He's always tackling idioms, scores, subjects that extend him in new directions.
It was a courtesy that she was not obliged to extend him.
"Hopefully we could have some success and then extend him again.
