Agreed: night lights are a VERY good idea with cockatiels, just make sure they are very dim.
Agreed: Lots of fresh food including sprouts, shy away from too much dry seed, best to feed it only as treats.
Agreed: Get two babies of the same gender, male is probably best to avoid egg laying. Getting 2 of different genders will likely lead to inbreeding even if you have no intention of breeding them.
I do not agree, however, that you should only get one. Two hand fed babies handled often will stay tame, and be much happier when you are gone than one bird would be. Just be aware that they need more of your time, not less, and that they may not continue to get along and may need separate cages in the future.
Make sure you have lots of toys, and I mean CHEW TOYS not plastic ones, and no mirrors. Foraging toys are ideal! Check out the internet on how to sprout seeds - I do my regular bird seed and a few extra goodies. Brush up on what foods are not safe for birds, such as avocado is poison, and so are raw beans.
STUDY YOUR BIRDS. Yours, not the internet. Learn to read their body language, learn what they like and what scares them.
I suggest getting two Aviator Harnesses before they even come home, and watching the whole instructional DVD. A bird that can go out safely is a happy bird
On that note, read up on the whole wing clipping issue before you decide. Read both sides! I suggest reading things by Dr. Steve Hartman of Parrot University in Ohio. Read especially his article on "thinking on the wing" I suggest reading these things before your babies come home. If you decide to leave your birds flighted, make sure the breeder knows that well in advance. If you decide that your birds are safest clipped that is your choice, just be aware that CLIPPED BIRDS CAN STILL FLY AWAY under the right circumstances, and it has happened to me. Heartbreaking.
Prepare your family! INSIST on people closing the doors, turning off ceiling fans, etc. If possible, hang a curtain between the living area and kitchen that can be closed while cooking. Things like that. Hide all exposed wires in whatever room the birds will live in.
Good luck!