What is the role of "when" here? Is it common to express condition using "when"?
"When" here is a conjunction. Another way you can think of this sentence is, "Woody, who needs a kid's room if it is possible for you to have all of this?" This sentence is not a conditional sentence because conditional sentences give a hypothesis and conclusion, and this one does not. Instead, this sentence is saying that "all of this" (meaning the amusement park) is better than a kid's room.