If you don't plan to breed, spay or neuter your puppy. Letting children see the miracle of birth is not a good reason to breed your dog; only serious breeders who have the desire, expertise, and time to breed well should breed at all.
Spaying your female dog can help to prevent cancers of the reproductive tract, including breast cancer, and will decrease the incidence of reproductive infections. Neutering your male dog will prevent testicular cancer and can decrease the incidence of prostate problems. The incidence of certain behavioral problems has also been shown to reduce when dogs are spayed or neutered.
The decision to spay or neuter your puppy is one of the best decisions you can make for its well being. Your veterinarian can discuss with you its benefits and the best time to schedule the procedure.