I think I watched this in the mid 90s. A group of kids are supposed to meet a paleontologist, I think at a museum. At the meeting place, they find a message from him (and I think a broken crate and dinosaur footprints). They follow the clues, learning about dinosaurs along the way until they reach the final clue, whereupon the paleontologist speaks to them from the shadows and then steps out, revealing he's a dinosaur. I don't recall if he was from the start, or was somehow transformed. The dinosaur looked computer-generated, but pretty realistic, maybe reddish colored? He was bipedal, about human sized, built kind of like a raptor.
This mostly describes the educational short Dinosaurs, Dinosaurs, Dinosaurs from 1985, where a young man called Eric goes to a museum and a clerk hands him a message from his friend Gary who's supposed to put on a dinosaur show with him. Turns out Gary's turning into a dinosaur so Eric goes looking for a cure, teaching us about dinosaurs along the way.
In the end, his friend emerges from behind a wall and reveals that he's now a reddish, bipedal, human-sized dinosaur. But there's no group of kids (though the clerk does call Eric a kid) or a broken crate AFAIK, so either you remembered that part from somewhere else or I got this totally wrong. ;)
You can currently watch the whole thing here, and here's the preview: