Howdy,
I'll be staying in Fuerteventura and then Lanzarote. Is there any way to charter a flight over the newly forming island/tail of El Hierro? Are there other volcano tourists interested in joining me? Would it be cheaper to take a ferry to Tenerife and then to El Hierro? How much would that run? How much time? Is La Restinga open again yet? In general, what is the best way for me to get to see the action?

The best way is to fly with either Islas Airways or Binter:
http://www.bintercanarias.com/
http://www.islasairways.com/

Unfortunately inter-island flights are very expensive to non-residents.

La Restinga is open again, I was there last week.

Awesome! Was anything volcano-related visible from La Restinga?
Are there charter flights available, or hot air balloons?

Hi, the only thing visible was the "green stain" in the sea 2km from La Restinga.

The sun glare off the sea means that you can't see much at midday or early afternoon, so you should probably go either early morning or late afternoon.