Pros

• Children can make and maintain family friends saving the working parents lots of time;
• If you keep your child well studied-up and send them to school every day, they sometimes get §100 from grandpa, at your disposal of course;
• Children can paint, you can sell their paintings;
• Each child you have reduces your household bills by about 10%. Go figure.
• Children are not expensive. Providing you serve good meals (§20 for 6 servings) a child will only eat one or two plates per day.
• Children can clean, wash dishes, make beds, take out the trash etc. My Sim-son cleans the bathroom and my Sim-daughter cleans the kitchen every morning before my Sim gets out of bed.

Cons

• They take up precious bathroom space as they will not use the bathroom if any other Sim is in there too;
• The three days of infancy are absolute torture for the caring Sim;
• Children love to run around in wide open spaces, often getting in another Sim's way and wasting precious time;
• You have to be sure you cook a good breakfast and get any children off to school every single morning. You also need to monitor their grades and if they slip, convince them to study;
• You have parents of your Sim-child's friends coming over to your house at all hours to collect their children.

Conclusion

Sure Sim-children cause a bit of trouble and require a little extra care but a house just wouldn't be a house without of couple of rug-rats.