First off something should be done. Try all you can to get the spca to get involved. The parents should understand the responsibility of owning a pet. Some one needs to take responsobolity here. Good on you for doing that.

The part I am troubled with is that you told him to have the animal put down.
As you stated you are not an expert. In my opionion you MUST be an expert to give such advice. The FIRST thing that should be done is take the animals to a reptile specialist vet. Please unless you are 110% that is what needs to be done do not give such advice.