Well, Serena would probably be over the moon. She's always been close to both Dan and Blair and would see this as a wonderful union. She'd be there for Blair during the pregnancy, helping her with shopping for baby clothes and giving her advice. Nate, on the other hand, would be more practical. He'd offer to help Dan with any financial or housing arrangements they need to make for the baby. And then there are the more catty friends, like Penelope and Hazel, who might be jealous and make snide remarks about how Dan and Blair got pregnant so quickly, but deep down they're just envious of their relationship.
It's hard to pinpoint exactly where Gojo is at any given time in the manga. His whereabouts change as the story progresses and different scenarios unfold. It could be in a supernatural realm, a mission site, or interacting with other characters.