For Kittens:
* A litter of kittens is the most common and widely accepted term.
* A clowder of kittens is a less common but more whimsical option.
* A kindle of kittens is another alternative, though it's less frequent.
For Puppies:
* A litter of puppies is the most common and widely accepted term.
* A pack of puppies is another option, though it's more often used for adult dogs.
* A whelp of puppies is a less common but more archaic term.
Ultimately, the best collective noun to use depends on the context and your personal preference.