Just also thought of tea-towels for sale - with paw-prints on them or with pictures of the animals.
Children and animals are cute together too, so how about pictures of the animals in simple line drawings by children and then transfer these on to tea towels, cards or calenders?
Perhaps not for this year as it might be too late, but if you approached a quilt group or embroidery group perhaps they might be interested in donating a hand-made item and then you could have a raffle for it to raise funds.
Also, what about having your own 'doggie blanket' or 'kittie blankets' for sale on behalf of the animal welfare groups? These could be fleeces with paw prints or bones or fishes on them? Although this would require some inital investment, it might generate ongoing interest.
Before i go, just also thought of a photo competition for a pet with different categories - cutest, funniest, most original etc. Ask permission for the photos to be used in future promotions and have an entry fee, with the prize being something like a trip to a grooming salon, or a free week by a dog-sitter or cat-sitter etc, or a gift of pet food (and see if a company will sponsor the competition).