Do you have children that like science and technology? Are you in Yokohama? I have just the place for you!The Mitsubishi Minato-Mirai Industrial Museum (wow, what a mouthful) is located right next to the Minato Mirai shopping complex, Cosmoworld, and provides a fun (if simple) look at the industrial technology behind the future.
There isn't much actual science explained, but this museum is a great way for kids to interact with scientific principles, especially in industrial situations. Most of the visitors seem to be younger children, though the adults there were having fun too. It's a nice diversion from Cosmoworld and the mall nearby, and with young elementary students, families could probably spend a few hours here.
The museum is located right next to the Minato-Mirai station and mall, across the bridge from Cosmoworld. It's open 10-5 Tuesday through Sunday, though there are three weeks (including New Years) where the museum closes entirely, plus a few other days here and there. It's important to check the calendar on their website for details. Admission is 300 yen for adults (less for children and seniors, of course).