Has anyone ever acted as a 3rd party observer in a child visitation setting?

Short background:
I have a friend who went through a very messy divorce. While he was married, they had 3 children (16, 14, and 12) the oldest of which was born with Cerebral Palsey and is permentantly in an electric chair. The divorce was quite a messy one. She had custody of the kids for the past 6 years and he just got custody of them due to her “failure to protect her children”. Apparently her current husband assaulted one of them so Child Protective Services pulled them and awarded temporary custody to my friend.

My situation:
The ex-wife currently has visitation rights with her kids equal to one hour per week in a public place with a non-related 3rd party required to be there to act as an observer to make sure nothing bad is going on.

I’ve been asked to be that 3rd party, and I’ve accepted. I’ve been told that this would only be once per week for a month until they have their next court date (apparently she is trying to legally get her kids back), but it could be a little longer.

What I would like to know is if anyone here has been in this situation before? What was your experience like? What were you required to do other than just observe and make sure the kids were ok? Were there any situations that occured with the visiting parent that made you uncomfortable? If so, what did you have to do? Did you have to file any reports to Child Protective Services? Is there anything I should be aware of?

Anyone’s insight into this would be greatly appreciated.

Thanks.