A therapy dog claim is frequently used as a scam. I was told by the rangers on the San Juan that they have to be an actual 'service' dog. A service dog is a dog that performs a duty to aid a person with a disability.
Scamming the system, or trying to scam the system as you are trying to do makes it harder for those with actual disabilities from being able to bring their actual service dogs on rivers. Someone with epilepsy could not safely go down a river without their dog who is trained to recognize when a seizure is about to happen, allowing them to get in a safe position to avoid injury.
It is illegal to represent that your dog is a service dog when it is not. If enough people do this, they may make it illegal for any dog, legit or not, to go on any rivers, thereby making it impossible for those with disabilities to go on river trips.
May the wind be always at your back,
May the sun shine warm upon your face.