Does this sound like a good start to ideas for my documentary?

That sounds awesome. You could do a montage at the start with shelters and abused animals with music. You could start by driving around looking for strays, talking to shelter owners, doing interviews all filmed of course, however if you will be filming or "outing" someone abusing animals you must blur their face etc.

Good on you for doing this.

Best of Luck!

Get the Obama administration to regulate who can own dogs and require that regular reports be submitted by each dog owner to be reviewed by a panel of experts appointed by the administration. Of course each dog owner must pay a fee for this service. Of course this service will benefit the general public and will save them money in the long term which will more than offset the short term increased taxes to pay for the new government agency to develop and administer the new regulations.

start by driving around your neighborhood and look for strays, neglected pets in an unsafe environment. film the locals leaving their pets out in the rain, sleet or snow with out shelter or food and water. that may be easier for you