“ The Mauritshuis museum, isn’t large and is quite special. There are several of Vermeer’s works there including “ The Girl with the Pearl Earring.””
The Girl with the Pearl earring is currently in the Rijksmuseum together with the other 2 Vermeers. The Girl with the Pearl earring returns to the Mauritshuis early on April 1. The other 2 Vermeers remain in the Rijksmuseum in Amsterdam until the end of the Vermeer exhibit in June. Apparently the OP is here before the Keukenhof closes which is in mid May. So depending on when exactly they’re visiting there is either only 1 Vermeer in the Mauritshuis or none at all.
To answer the OP’s question; depending on your interests and when exactly you are here, there are lots of places to visit. Several nice places have already been mentioned, but if you tell us more about what kind of things you like to see and do, we may be able to give more specific recommendations.