[The Squatter of Amon Rûdh]

It gives them a choice, but it's not the same one that Elrond and Elros were given. Elladan, Elrohir and Arwen can go with Elrond beyond the circles of the world or remain in Middle-earth and live a mortal life. Where they are determines what happens to them, whereas Elrond had the fate of the Elves wherever he was, just as Elros was mortal wherever he happened to be living.