They should get a +1 to thier AR , but only if the other toons are at max AR already, otherwise it’ll go to a random character.
This ^^ - If you send it with other that are maxed it can only go to the one you want.
The way I understand it, it doesn’t go to a random character, it goes to the lowest AR level character. But either way though, safer to send all max chars and the character you want the AR level to go up.
Long time to be without a legendary toon though