No. They want the islands as a means to claim the surrounding waters, which which have a lot of real and potential value in fisheries, sea lanes, and offshore oil. The islands themselves are not very valuable.
... also worth mention: they're not too happy with the US Navy operating freely within the South China Sea, even if the rest of the world calls it "international waters". The red line in the map is what they'd rather keep a powerful non-China navy out of, for both defensive and offensive reasons.
