Hello

and Welcome To BYC!
You might also like to check out the BYC Learning Center, lots of good articles on all aspects of chicken keeping.
https://www.backyardchickens.com/atype/1/Learning_Center There are several articles on the benefits of having chickens.
With very young children it is usually recommended to avoid roosters, they can be dangerous.
Cats can be a danger to chickens, especially feral cats ... usually pet cats won't really bother adult standard chickens but would take chicks.
Hawks can be a problem, a covered run is the best protection, if you have dogs they are often good at keeping hawks away, nice thread on dealing with hawks
https://www.backyardchickens.com/t/741631/hawks-and-how-to-stop-them
It is amazing how many spouses do come to like chickens once they are there, if it isn't the cute chicks and how personable chickens are and how much the kids like them, the fresh eggs are usually a winner.
Here are a couple of links to some nice chicken breed comparison charts you might like
http://www.sagehenfarmlodi.com/chooks/chooks.html and
http://www.albc-usa.org/documents/chickenbreedcomparison.pdf when you have narrowed down your choices, don't forget to check the BYC Reviews section for member reviews on the different breeds.
For pets,especially for children, Cochins are a popular breeds, they are not very good egg layers but are very friendly and often go broody if you would want to hatch eggs.
So far as more layer breeds go, for egg numbers alone, the Red Sex Links like your Golden Comet are probably the best brown egg layers around, But, they are bred for high production early and are often short lived and prone to reproductive problems.
If you want breeds that don't lay quite as well but will lay for a longer time, Australorps and the Plymouth Rocks you mention are two good choices, some other popular ones are Orpingtons (lots of people really like these, great pets though broody), Sussex, Delaware and Wyandottes are breeds that are usually pretty easy to get along with, they all lay different shades of brown eggs. The Easter Egger, often sold as Ameraucana by hatcheries, are a fun breed because they usually lay green/blue eggs, kids usually find them neat, and they tend to be very nice birds, and then there are the Welsummer and Marans for dark brown eggs.
You might also like to check out your state/country thread to see what people in your area have or what would be available
https://www.backyardchickens.com/t/12049/ohio-come-on-buckeyes-let-me-know-your-out-there