I think you've made a very sensible decision, Inewv5! The half is definitely not a stretch (at least I don't think so), and considering what you're currently running- it should be VERY do-able! I just finished the same Hal Higdon progam you're referring to, and it was quite managable (but, I guess it would've helped if I'd actually gotten in all the suggested runs ).

Good luck! And you know, you can always do the half early, then plan for a late fall/early winter marathon later in the year...