Hi Afish -
Couple of thoughts:
1. If you go to this page:
www.ptotoday.com/ubb/ultimatebb.php?ubb=forum&f=10
... and change the "show topics from" button (on top of page) to: "the past year", then you'll see a whole slew of threads on this very topic. I bet they'll be helpful.
2. If it were me, then I would spend down the $$ in your PTA account. You could buy something for the school or fund an Arts program, etc. To me, it's an easy way to avoid any of the $$ hassles that soemtimes come up upon dissolution.
3. I'd start your PTO (completely independently of your PTA) now. Get a Fed. ID #, get some bylaws and officers, maybe even apply for your 501(c)(3). Your current PTA and your to-be PTO are completely separate. Some folks make the mistake of thinking they can't possibly start the PTO until the PTA is all done. That's not true and -- in my opinion -- not wise.
Finally, it seems that you're in a less sticky situation than some others. You haven't paid your dues or otherwise acted like a PTA for several years now. I'd wager you're a group "not in good standing." It's not a far leap from there to done.
Good luck,
Tim