Wow, you have quite a project on your hands!!!
If you're well along in your 3D skills, you might consider getting ahold of
Blender 2.6. Blender is free (open sourceware) and has all the "character rigging" features you'll need to bring your Fox and Duck characters to life... not to mention, the community is big enough to increase the odds of your finding "off-the-shelf" characters you might be able to buy or lease. The biggest downside to Blender is its maddening complexity and visual overkill.
AC3D is ideal for CREATING a character, but doesn't help you animate it, unfortunately. Blender is a complete CGI system.
(
Sorry, Andy: I'm not trying to steer anyone away from this product, just informing someone of what's out there for his particular problem. Do rest assured that I also steer people to THIS excellent program whenever I get a chance! 
)