Germany with kids

What do you consider kid friendly? What do they like to do? What are their interests?

They like outdoor activities - biking, roller blading, sometimes hiking. They liked to go to interactive museums - science, natural history, etc. I'm hoping they'll enjoy seeing some castles, medieval cities.

oops - and by kid-friendly...places that don't require the patience an adult might have. They probably couldn't see as many historical sites as I might like to. Nor will they likely be able to spend as long at those sites as I might like to.

If your kids like being active then try out one of the many climbing parks like these ones: http://www.kletterwald-neroberg.de/information-in-english.html http://www.kletterwald-taunus.de/ http://www.adventureforest.de/ There are very popular in Germany and quite affordable, usually around 10-12 Euro for 2-3 hrs per kid. My kids just love it and wish we could find anything comparable around here. They also like the Dialogue Museum in Frankfurt where you can experience absolute darkness, just like a blind person. There's even a restaurant where you eat in the dark. http://www.frankfurt.de/sixcms/detail.php?id=5021811&_ffmpar%5B_id_inhalt%5D=5021033
http://dialogmuseum.de/

Opel zoo is close by. If they like amusement parks, look up Taunus Wunderland. Hessenpark is a open air folk museum, and although it isn't the best of it's kind (only about half of it is completed), they might enjoy a visit. Finally, a popular family hike nearby is up to the summit of Klein Felberg, which is the most prominent mountain just to the north.

What are your travel dates? Might be a fest in town or near-by. Second the Fun Forests. The one in Wiesbaden is really good and lots of fun. Most kids like the chair lift at Rüdesheim. Take the train or boat on the Rhine and visit Rhinefels in St. Goar. Your kids will love it. If you have a car available, Hessen Park is pretty interesting and the kids can really run free here. They have animals and demonstrations of all kinds. http://www.hessenpark.de/index.php?id=english The Saalburg (a reconstructed Roman Fort) near Bad Homburg is also interesting. http://www.saalburgmuseum.de/english/sb_en_home.html A closer castle ruin would be in Eppstein, just a short trip away by S-bahn.
http://www.eppstein.de/staticsite/staticsite.php?menuid=160&topmenu=93 Interactive museums in Frankfurt would be the Film Museum, the Communication Museum, and Explora. The Senckenburg Natural History Museum is also quite good. On Sundays, the Antique Tram museum is popular kids, as they can climb all over the trams. If the weather is nice, the Palmengarten has lots of playgrounds, as well as a small train. Some of the adventure pools can be nice to go to, especially if we have some bad weather. Rebstock Bad in Frankfurt is a good one.

Thank you for all the tips so far. To answer a question about when...we will be there in July.