Sorry for the quick reply above. Peabody Essex is Salem's gem; it offers a good view of the city's maritime history and has lots of art. Plus Yin Yu Tang, the Chinese house! There are two videos that are worth seeing, one about the process of disassembling the house in China and reassembling it in Salem and the other about the family that lived there for many generations.
You might also consider touring the House of Seven Gables and/or seeing one of the two new 30-35 minute movies about the Salem witch trials. The Salem Witch Hunt: Examine the Evidence is shown at the National Park Service Visitors Center across from the Peabody Essex; I've seen it and recommend it. The True 1692 is shown at CinemaSalem, but may be offered only occasionally now that October has passed; I haven't seen it yet.
If you have a chance when you're in Beverly, take a ride up coastal Route 127. Even if you only go as far as Manchester (or even Beverly Farms), it will give you and your daughter a different glimpse of Beverly and nearby.
Hope you'll have a great visit!