When it comes to the children and their interaction with the evaluator, the primary lesson is simple: let the kids be themselves.
They don’t need to be prepared to answer questions. There is no coaching required. They don’t have to act differently. They don’t have to dress differently. They just need to be as normal as they can be. They need to be who they are every other day of the week… with the exception that someone they don’t know will be there and may ask them some questions. Encourage them to be “on their best behavior” just like you would with any guest coming to your home. Be normal. Be natural.
The only instruction you may be given would be to encourage the children to do whatever playing their going to do in the room where you’re having your interview with the evaluator. The children may be asked questions while they are playing or you might be prompted to have the kids sit down on the sofa/chairs for direct discussion with the evaluator in your absence.
If the time with the children is done at the office, it’s essentially the same thing only the CE will likely have a bucket full of toys for the children to play with. The children will be encouraged to play and you will not be encouraged, but you should also interact with the children as you might normally do.
Please remember, the evaluator is unlikely to explicitly state so, but they are observing your interactions with the children on a very, very limited basis. So, no matter how short in duration or forced in may feel, do interact with the children when you see an opportunity present itself. It may be guiding them through a disagreement… if you have only one child, grab a toy on a lark and partner up with them… help them build something… guide them through a problem solving exercise… work on a puzzle… if they should grab a book, read it to them for as long as the evaluator may allow.
In addition to talking to you (and your ex) together with the children, they will very likely also speak to the children alone. All you can do is pray during those sessions that they answer whatever questions directed at them in a way that isn’t detrimental to your case.
Prepare in a way that keeps the children at ease.
Go through it in a way that keeps the children at ease.
Congratulate them for a job well-done when it’s all over.