No, he wasn't joking, he just was expecting Sora to punch his shoulder and laugh at him.
"Whatever," Riku agreed with a grin.
"Punch sounds good." As did checking to make sure that Gokudera wasn't getting into a fight or anything.
Actually, it looked like the little guys were over by the punch bowl too. "Hey guys," Riku said, putting his arm around Sora's waist causally. "Having fun?"