I've just got two Siamese Kittens, I would recommend taking them to the Vets when you can, just so they can give them a good going over, both of mine had problems within days of bringing them home, and after a week of treatment they are so much better.

We have 3 litter trays, 2 downstairs and 1 on the landing, you just never know.

For feeding we give them both Purina One Dry food, this really helps them to drink plenty of water, and we also feed them Felix as good as it looks pouches.

Just enjoy them, they are so funny, and like kazijay has mentioned, loads of batteries for your camera.

Oh, and they'll be into everything, like walking over the keyboard when your trying to type,
Good luck with your new kittens.