I understand your desire to start clinical in the fall. My guess is that FNP does the same thing with the specialty classes and only offers them once a year. It's very tempting.
The problem with taking on that many credits a semester as a working adult is that you leave yourself no wiggle room. If the car breaks down, a kid gets sick, or the schedule at work poses a conflict, you can't flex anywhere to come up with a solution. And make no mistake, the school does not care about whether you work or have outside commitments. They spell that out in the student handbook.
If you take one course a semester, you can start your specialty in fall of 2012, and you'll have given yourself half a chance to be ready for it. No need to make yourself insane trying to do it all at once. That extra year will go by pretty fast, and you won't be miserable and stressed out all the time. Just sometimes.
Best of luck, no matter what you decide to do. And Happy New Year.