Driver wrecks car and leaves behind two injured passengers. Can I charge one count for each passenger?

You might look at Huffman v. State 267 SW3d 902, a CCA opinion from 2008. It has a pretty good analysis of this issue and I believe will allow you to charge in the way you are hoping.

Also see Spradling v. State, 773 S.W.2d 553, 556-57 (Tex. Crim. App. 1989).