the kid was effectively long gone and keeping a corpse warm forever isn't really in anyone else's best interests

I agree with this, and if the doctors aren't being honest about this with the family then they should lose their medical licenses. That said this is a call the family needs to make. That the family may make a retarded choice isn't a good reason to deprive them of their choice. Remember the Obamacare death panel debate? This is what the Right was worried about.