Hi blackriderx,
If you have confirmed that the slats are 3" or less apart then it should be fine for an all latex mattress.
It seems that some of the west elm slats are 4" apart (see here) which is a little more than ideal spacing but it also seems that some of them may be less than that (based on the picture here which has 16 slats) so I would check to confirm the distance between the slats in the bed you are ordering.
Phoenix