I am no vet, but we have had 2 dogs with Parvo in my life (1 was a stray we took in who presented with Parvo just a few days after we took him in) and they were NOT playful once the vomiting and diarrhea started so I am hopeful that it is something else like coccidia as someone else posted. Both of ours with Parvo had virtually no energy and seemed depressed which I believe is typical. I think the fact that yours are playful is a good sign.
Also, if your pups are at home then your vet is NOT treating as if it were Parvo. If the vet were treating as if it were Parvo they would be in the vet with an IV IMO. You don't send Parvo dogs home until they are over it.