I love the toddlers! I don't think they are challenging at all but can be time-consuming. What I find challenging is adding a dog to the family with toddlers and kids because the dog needs more attention than the kids do and 9 times out of 10 the dog will run away and the family will be sad and the dog will come back for a few days just to run away again and the real kicker is that the dog has a high relationship with all the family members. My sims just don't have time between their jobs and three kids to give their dog a lot of attention. So now I give my sims cats.