For those in a simliar situation, we have been reliably informed that the very best food for a Maine Coon kitten is Royal Canin Kitten 36. It's a complete diet dry food which is good for the teeth and keeps well. You can also feed a small amount of wet food (good for kidneys and if your kitten doesn't drink much) but don't leave it out because it goes off very quickly. Our breeder recommended MPM Applaws for kitten wet food.
As for litter, World's Best is recommended becuase it's totally natural and can be put down the WC. It's a clumping litter so is easy to keep clean, and you won't use as much as with other litters which will need emptying more often.
Dry Food: Royal Canin 36
Wet Food: MPM Applaws
Litter: World's Best
All above available from most pet stores, although your breeder may also be able to supply you. Or shop from our Maine Coon MAD Pet Store.