I believe that you can bring the firearms over the border to an FFL in MO and let them complete the transfer.
It would be a nice present to say "Let's go looking" and stop in at the FFL with your Dad and brother.
I would set up with the FFL first.
"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
Life Member NRA
Life Member NAHC
Former President of the ECPT (Eifel Combat Pistol Team)