N.G.
First off, I don't let my kids make decisions about pets, because inevitably I will be the one caring for the pet. So unless you are willing to assume all the work, don't keep the cats. If you are, you will need:
Vet visit (checkup & shots & de-worming)
Flea medication (preferably prescribed by vet)
Collars
Litter box
Kitty Litter (multi-cat to control odor)
Poop Scoop
Kitten toys
Scratching post/climber
Food (ask Vet which is best)
Treats
Brush if either of them has long fur