update: son's birthday was a big success even though he only got the Mystery Machine with Fred and Scooby. We just used the other imaginext figures as fake monsters (the headless horseman guy is perfect, and the pirate cove playset looks exactly like a scooby episode). Too bad you can't get the whole gang in one package, but it works.
The van is pretty cool even though the action feature is dumb. You can stage some scooby pratfalls on it.