Did Elladan and Elohir Die or go to Valinor

[Legolas]

But why would they get the choice of Mortality or Imortality and not the children of Elros? Now that I know its undecided and a big issue, my opinion went in between.

Because they were the children of entirely mortal parents. Elladan and Elrohir had a wholly Elvish mother in Celebrian, and thus a renewed Elvish strain. Tolkien says so in Letter No. 153.:

The view is that the Half-elven have a power of (irrevocable) choice, which may be delayed but not permanently, which kin's fate they will share. Elros chose to be a King and 'longaevus' but mortal, so all his descendants are mortal, and of a specially noble race, but with dwindling longevity: so Aragorn (who, however, has a greater life-span than his contemporaries, double, though not the original Númenórean treble, that of Men). Elrond chose to be among the Elves. His children - with a renewed Elvish strain, since their mother was Celebrían dtr. of Galadriel - have to make their choices.

He also makes it clear that Ell./Elr. had the oppurtunity to delay their choice at least a little past the departure of Elrond with "[the choice] which may be delayed but not permanently" and other lines.

There are so many threads about this. Searching would bring you results instantly. There's even an article about it:
http://www.barrowdowns.com/faq_halfelves.asp

[ April 24, 2003: Message edited by: Legolas ]