Poland is not particularly well suited to traveling with small children. Distances between cities are relatively far, and kid-friendly sights are few. To make things worse, museum exhibits tend to be static rather than interactive (on the plus side, many museums do not charge admission for children 5 and under). It pays to read up a bit in order to entertain the kids with tidbits of historic tales. Among Polish cities, Torun is compact and easy to manage, with tales like the Teutonic Knights and Copernicus, and rewards like a trip to the Gingerbread Museum to keep children motivated. Malbork Castle will certainly set a benchmark for kids in sizing up any castle they are likely to see in the future. For real interactive family fun, try kayaking in Mazury and Suwaki, or rafting down the Dunajec river.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.