A.L.
If you'd like to relate it to pet care - maybe contact your local ASCPA to see if they could come in to speak to the kids about it taking care of animals and how their business works.
Then maybe have the class make rice socks for the new puppies and kittens that can be warmed in a microwave and then placed into their cages to keep them warm. My daughter's girl scout troop did this for our local chapter last year, and it was greatly appreciated. Everyone brought in two old or outgrown cotton socks, decorated them markers, poured about 1/2 cup of white uncooked rice into them, then tied off the end with a grosgrain ribbon (adults had to triple knot these). Your cost in this would be for the rice and ribbon - so under $10 for the whole class.
Good luck and have fun!