I don't think Piping plovers would be there this time of year.
A juvenile Piping Plover is only smaller then the adults for a very short period of time. Towards the end of the nesting season, juvenile Sandpipers and Plovers are the same size as the adults. Their plumage or color is different but they are the same size.
Without looking at my reference books, I think Piping Plovers are around 5 1/2" Long from tip of beak to tip of tail.
Sorry, should have checked date of post. They would migrate in Early August to mid August where you saw them.