Campbell bagged his third goal in five appearances since joining from QPR to seal Saturday's 1-0 win at Birmingham and end Ipswich's sorry 12-match winless run in McCarthy's first game at the helm.
The striker is a month into his three-month stay at Portman Road but McCarthy is already looking to tie him down longer.
"He's a goalscorer, there's no question about that," McCarthy said. "I'll have to be talking to the powers that be and try and keep him because he's a great little character. He's good around the place. I thought he played well."
Midfielder Wellens is another of eight loan players in total at Ipswich, although his month-long stay is now at an end.
Speaking on Saturday, McCarthy added: "I thought Richie was terrific. I hope I can keep him, I'll have to speak to Nigel (Pearson, Leicester manager) about that."