I think the order says they have to appear with the kids at either the court or the state health and welfare department location in Rexburg. That said, I'd think the attorney could potentially convince the judge to do something less than that if they wanted. (All MOO and I have no specialized knowledge, so may be way wrong.) If, for example, they said "the kids are both in Europe attending a school and we, Chad and Lori, are as you know, in Hawaii, so the cost of us bringing them in would be very high, plus JJ is doing well and this would disrupt things" then maybe they could convince the judge to do something different. I'd think just a video would not be enough (how do we know it is current). At a minimum I'd expect the judge would want to be able for him and others to ask them questions. They might also want them to be seen in person by someone unattached to the story and probably trustworthy to make sure they weren't being forced into giving the "right" answers to his questions.
But just as I've wondered since the beginning, if the kids are alive and okay, making this go away is very much doable and I suspect fairly easy. So either the kids aren't okay, or they're afraid the kids being in a position to talk would be an even bigger problem for them, or they're convinced that we're close enough to the end of the world that it won't make any difference by the time it all comes crashing down on them.