These have the same reading as ひろげる, but a different kanji. Is there any variation in connotation between these, or is it just variant spelling? Is 広げる then, as I believe it is, the more commonly used of the two?
Although Shinmeikai and Daijiten have these as being exactly the same, Meikyō provides a narrow band of usage for 拡げる. [This answer was rewritten to reflect this.] 拡げる is used for "broaden" or "enlarge," but not for "unfurl". 広げる can be used for all three.
There is another kanji associated with ひろげる, 展げる, which is used only in the sense of "unfurl". It's comparatively rare.