Cat, dog, ball, block, flower, bird, rabbit, feather, rhinoceros.
(That last... why not challenge them?) ;)
Added:
A-Z
Apple, ball, cat, dog, eagle, flower, giraffe, hat, ice, jumprope, kite, lamp, mouse, nut, otter, peacock, quail, rat, snake, teaspoon, unicorn, vase, water, xylophone, yak, zebra.
(Maybe find toy models of some of the animals--like, if you use rhinoceros, it might not be good to put them in with an actual rhino!)