Congratulations on your new puppies. It is normal for their stomachs to look large after eating. They should not however, look bony. Have you dewormed the puppies yet? 85% of all puppies are born with roundworms and need to be dewormed. Your veterinarian can give you some good dewormer for the puppies. There are over the counter products as well, but some of them only cover roundworms and not other parasites. No matter what, you should bring a stool sample in to the vet for a check. Some worms are transmissible to people and you want to make sure that the puppies don't have any parasites.
Please let me know if you have any questions. I hope this answers your question.