For a toddler? Welllllllll... Guinea pigs are
work. They take a lot more attention than you would think, and you have to get at least two. Unless they are raised together, females tend not to get along, so you need to put a bull in there with them to keep them in line (srsly). Now you have three. You need to make sure that either the male or both of the females are fixed, or you will soon have more than three (ask me how I know). Also, verify that none of your females are preggers before bringing them home, or you will have a surprise on your hands one morning when you find out your pigs have shrunk. They eat a lot, and you'll find yourself preparing vegetables day and night. And, the poop. My God, the poop. You need a strong mini-vac to keep up with their butts daily. Like
@H. Vachon, they have no internal sphincter, so the poop just literally falls out of them as they scurry around. Shop Vac works better, but you chance sucking up a furry potato if you aren't careful.
They are great little pets, but do require a lot of attention that most are unaware of before they commit themselves (or someone else).