What do we do in vernazza in july?

Me and my niece are going to italy in the summer. We are going from pisa to la spezia. We are staying there for 2 days. After we arrive in the morning on the first day in la spezia, we are going to vernazza. Our plan was to do the first day in vernazza and the second in la spezia. We dont know how long we will be in vernazza as it is really small and we dont really have an idea what to do. Are there any recommendations? We are only using train as transport.

Our trip is: Pisa 1 day Vernazza 1 day La spezia 1 day Lucca 1 day Florence 2 days Montepulciano 2 days Arrezzo 3 days