During my daycare years, we had cats, dogs, hamsters and bunnies.
Dogs can be high maintenance but were much loved by dcks(not to mention parents were glad for the exposure at dc so they didn't have to get one Lol), cats never liked to be handled much
, bunnies were wonderful pets as long as they tolerated being held because that's what kids want to do, and hamsters were a lot of fun to watch but mine used to bite when I'd try to hold them so dcks never got that opportunity. The dcks especially loved things like hamster wheels, and balls(the kind you put them in and they can roll all over the house) and all the fancy tubing/connections you can buy.
I know a former dcm had a hermit crab for her dd and they really enjoyed it but said it took some care. I remember giving her some bigger seashells for it so they could watch it try on new houses.
I always fantasized about getting a mini horse for our backyard.