A joint legal custody plan should have a mediation tool (though I recognize many do not) for instances when parents disagree. Short of agreement through some sort of mechanism (formal or informal), in the absence of agreement, the court must step in to allow a parent to make such a decision. So you’d ask the court to let you make that choice.

There are complicating factors like schools, and TX and TN have different rules for vaccination opt-out for school. So it will matter, too, where the kids go to school (TX is more forgiving). Camps also present issues as if you want them to go to camp, it may be necessary to vac them, too.

If you have an attorney for the visitation dispute hearing, this can be wrapped up in the full set of issues. It may be that joint legal custody can no longer work for you both if you cannot come to these decisions jointly, so have a backup plan, too, if that is necessary.