With a chance of rain today we opted for some inside activities and decided to go to the "Centrum Nowoczesności" an interactive science center made for kids, but us grownups had just as much fun or more than the kids did. This science center is in an old mill building which has been renovated & put to good use. The same has happened in New England, where they have renovated old mills and turned into useful space.
Surprisingly things where written in both English & Polish, so if you were visiting the area and want to take your kids to have fun, there will not be a language barrier, but I don't thiink the kids will worry about that, they will just have fun.