Kaladin is not a full Radiant yet, he has only said the first two Ideals of the Knights of Radiance. The first one being the "Life before death," and the second being the "I will protect people who cannot protect themselves,". Unless I'm mistaken, there are ten Ideals and the first two are generic for all ten groups of knights and the next eight are specific to each group. Also we don't know yet if Kaladin will even be a Windrunner because there are two groups of knights that have the ability to bind things.
It has to do with the double eye of the creator design on the inside cover of the book. There are ten groups of Radiants and ten Radiant abilities. Each group of Radiants has two abilities and each ability is used by two groups of Radiants. If you look at the design I'm talking about, then each colorful symbol represents a Radiant group and each black symbol represents an ability.
So unless there is something I haven't seen that Brandon or Peter has said, then we don't know if Kaladin is a Windrunner.
Also Beorc is right: Jasnah is Dalinar's niece, not sister. Aside from that, they are going to the Shattered Plains not to look for Ureata, but to study the Parshendi. I just read the last Shallan viewpoint chapter where they talk about leaving (p. 990, hardcover).