Our attorney told Mr. B that he should expect to be there no more than 1 hour but even it it's longer I think Mo would have no problem keeping it together.
Then there should be no problem at all if it's only an hour or so. And, for part of that time, his dad will be testifying. I think he'll find the whole experience interesting. He'll not only get to see our judicial system in action, but he'll see his father as a part of it, and that will make it special for him.
If he understands beforehand why Mr. B was asked to testify in this case, and what information he has to offer, Mo could probably better appreciate and understand the kinds of questions both sides are likely to ask his father and that would help to make it even more interesting for him.