I've seen a lot of little birds hop around. Not only are birds dinosaurs, but the particular birds I've seen hopping are very similar in shape to a T Rex.
My chickens run around very similar to the run we see of T-Rex/raptors in movies. They lean forward and low and run surprisingly fast for an animal with wings that they just tuck.
Yeah, that seems more likely from what I know about dinosaurs. Just saying, we already have birds who hop to compare to. The kangaroo idea just strikes me as silly