This posting is an effort to make sense out of some things that have been confusing me for a long time by constructing an admittedly highly speculative narrative. It draws extensively on information gathered outside the TOS boundary and is accordingly coy about certain names and descriptions. Please respect the TOS in any followup comments.
What Was The Plan?
OK, let's put ourselves in the shoes of Chad, Lori, and Alex up in Rexburg in early September. They still need a big score. We don't know why, but there are signs of some Grand Plan that requires upwards of a million dollars to carry out. They tried and failed to get this from killing Charles and so they have decided to murder Brandon and Tammy for their respective insurance payouts.
What About The Kids?
There's a problem: these actions will probably result in contact from the authorities and Tylee and/or JJ might break down under interrogation and spill the beans about the Chandler shooting. So the two children have to be isolated from the authorities.
The simplest solution, as noted here time and time again, is to just murder the children and bury the bodies in Yellowstone National Park. But maybe that is unacceptable, for instance by causing schisms in whatever larger group is involved in the Grand Plan. So for sake of argument let's say the problem reduces to one of hiding JJ and Tylee from the authorities for several months until the Grand Plan can be put in place. But making a pair of kids truly disappear off the face of the earth for a limited time in today's society is no easy task.
Does Being in Rexburg Help?
But by being based in Rexburg Chad and Lori had an option denied to most of us.
North of Yellowstone is an area of Montana that is very much a wilderness. If you put together zip code 59027 and the Western third of zip 59030 you get about 750 square miles with a population density (outside the two towns in the area) less than one person per square mile. Fly over the area with Google Earth and you'll see woods and clearcut fields crisscrossed with a maze of dirt roads and jeep trails and sprinkled lightly with individual houses and small compounds, some left over from a now-diminished New Age religious group that believed in building bomb shelters in preparation for nuclear war. A lot of empty dwelling places are listed for rent, and even more are probably available if you know who to ask.
Lori and Chad would then have to rent a cabin, or RV, or doublewide out on the end of a Jeep trail without leaving an evidentiary trail.
Could The Cox Family Help?
Here we enter an area that hasn't, in my mind, been given enough attention, and that is the politics of the Cox family.
That family has demonstrated an organized contempt for government authority, and at least one member of that family has impressive credentials to present to any like-minded individuals. And Montana is well populated with such individuals. It is plausible that, without any theology being involved, Lori and Chad could have had a suitably remote dwelling rented by a family member from someone with similar political views; someone who under no circumstance would cooperate with law enforcement, especially after being told by that third party the rental was to hide the children to keep them from being kidnapped by the government.
Wouldn't The Children Starve or Leave?
Being good preppers, Lori and Chad would have ready access to all the necessary survivalist rations and material to enable Tylee and JJ to stay out of sight with minimal or no contact from people who might be followed by law enforcement. And even if Tylee was not 100% sold on the idea of being isolated, being a city mouse out in the middle of the woods without even a compass (much less any wilderness skills) would be almost as good as a fence in keeping her and JJ from walking out to civilization.
Why Two Trips?
If (really big if) this was the plan, then after visiting Yellowstone on the 8th of September, Alex and Lori would have taken Tylee to the dwelling in the woods to get it ready and accept deliveries of supplies. (She was, by her own admission, used to being left alone at Alex's place.) JJ would have stayed visible in Rexburg to disguise what was going on and then been driven up to the dwelling by Alex sometime between the 24th and the 30th of September.
As I said, this is all pure speculation and opinion on my part. I have no evidence other than an absence of refutation. But I believe that this scenario, or some variation of it, is more plausible than one in which Alex kills Tylee in Yellowstone and then he and Lori wait two weeks to murder JJ (and dispose of his body) when they are in the middle of planning the shooting of Brandon and the attempt on Tammy's life. Sadly, most of Chad and Lori and Alex's plans went awry; and if this one did it would be just as tragic as if the children were murdered.