I keep the 'Legal Heat' App on my phone for quick reference to the gun laws in various States.
Unless otherwise prohibited...they could carry (in vehicle) in Texas under the Motorist Protection Act. Depending on what other States they were traveling through...similar laws may or may not apply.
https://apps.apple.com/us/app/legal-hea ... d499394939
Odds are....they would be better served with OC spray and be very careful about where (and when) you choose to stop.
Oklahoma, Arkansas and Missouri are all 'Constitutional Carry' States and they shouldn't have any problems carrying there. BUT Illinois requires the weapon to be unloaded and fully enclosed (read useless). There may finer points of the law or other restrictions that would need to be researched.