Congrats! I'm so excited for you getting your first kittens! Make sure when you get the litter to buy the regular clay (its really cheap, so you'll know it by the price difference) - not the clumping kind, especially if you put them in the bathroom or another smaller room. Because they eat their food and step in water, etc... then go potty. Then the clumping litter sticks to their paws, etc. When they are a bit older you can switch.

If you can't get to the petstore, your local supermarket or CVS has small plastic trays in their pet section that could fit into a carrier. The cake pans are a good idea too.