But the story doesn't have to stop there! Grandma & I have dealt with a similar situation , too.
Let me say right now; get an attorney experienced in family law, if at all possible. This can be a very difficult situation to maintain control of by yourself! And if not done properly, you could end up with the Grandson in a foster home!
I'm not familiar with Missouri law, but in Arizona there are two types of guardianships. One grants all the rights and responsibilities of the natural parents, but the parents may terminate the guardianship with very little legal effort and no proof that the situation has changed that caused the original granting of guardianship! Only a statement that they wish to terminate the guardianship!
The other guardianship is called "Permanent Guardianship" and can only be terminated by the court upon convincing evidence that the parents have changed the conditions which caused the guardianship to be granted originally. The court would have to see that this change of conditions has continued for a reasonable amount of time before granting the termination of Permanent Guardianship; and that is was in the child's best interest.
At the moment, it would seem that there is a measure of cooperation between the parents and the grandparents. But it will be very difficult to maintain that cooperation when the court battle starts! The Grandparents will have to try to convince the parents that this action will give the parents relief from the stress of caring for the child, so that they can concentrate on getting "their act together". And, the parents will need to be convinced that giving guardianship rights to the Grandparents won't result in their parental rights being terminated! Unless the court orders otherwise; the Grandparents may allow visitation as they see fit.
Anything the Grandparents can do to keep a spirit of cooperation will make things go a lot smoother.
** The information in my response comes strictly from my own similar experience and not from any knowledge of family law.**
However, I hope this will give you some insight as to what you are about to undertake! Good Luck to the Grandparents. I wish every child in this situation had family willing to step up and help!