Thank you so much for all the information; that is very helpful and just what I was hoping for!
I was also really interested in the light brahma. After all my researching, I'm thinking of getting a light brahma, black Australorp, bielfelder, and Easter egger, and hopefully 2 speckled sussex.
Congratulations! How exciting to get a flock. Your kids must be really happy

. Good idea to get six birds. I would get six to seven chicks. Inevitably and unfortunately some will die, some might be roosters (although I *highly* recommend getting sexed birds with such a small flock and if you're not zoned for roosters), and it's difficult to integrate new chickens into established flocks.
The breeds you're thinking of look great, are great layers, and cold- and heat-hardy. I also like having a mixed flock. I think it's more fun and you'll have a lovely egg basket. I would also recommend making a coop and run that is as large as possible. The ones sold as kits tend to house far fewer full sized hens than advertised.
Our Black Australorp, Rhode Island Reds, Orpingtons, Speckled Sussex, and Black Sex Links/Black Stars all have done well with successive blazing hot southern California summers. They are also really friendly. We have 9 month old Easter Eggers we love, too.
Here are some breeds we've found particularly quiet/docile that are consistent egg layers and mild mannered towards other breeds (a must if you live in a densely populated area): Crevecoeurs, Easter Eggers, Australorp, Orpingtons, Phoenix, Speckled Sussex, Barred Rocks, Faverolles, and Welsummers.
Loud, bossy, skittish, flighty birds (although totally lovable): Black Sex Links, Egyptian Fayoumis, Rhode Island Reds, Buff Minorcas, Lakenvelders
Let us know what you decide to get!