Interested in an intelligent, affectionate, self-cleaning pet that's suitable for your child? Get a rat.
No, really. While their sewer-dwelling, dumpster diving cousins have a bad reputation, domesticated (or "fancy") rats shouldn't be tarred with the same brush. Fancy rats easily learn tricks, love to play with their humans, and meticulously groom themselves. Like guinea pigs, they're very social, so getting a pair is probably your best option. Older kids can play with their pet rats unsupervised; younger kids should be attended, though that's more for the rats' safety than the child's (rats rarely bite). And they're decidedly low-maintenance: Aside from cage upkeep and daily feeding, rats just need regular play time outside of the cage.