Dude, your demo Reel is very good! How much can you charge will depend greatly in your location. For axample, here in South Florida, a motion graphic artist charges from USD $50 to $70 an hour, 3D animators vary but a bit higher than motion artists. Most clients like to pay per package, but is based on an estimation on the above hourly prices.
In other states such as NY, price may even double. Consider that the economy is really slow now so you may need to cut down a bit.
On suggestion....do two demos, one with the characters the other will the rest of your stuff. Your characters are good but your other stuff is way way better......
Hope this help.