Our first European trip with my 10 year olds was to a destination that I never expected to go to but Rick's book/show introduced me to the charm of the Rhine Valley, Germany. I was a bit apprehensive as we speak no German, no one I knew had been to Germany, but Rick's book/video showed such an enchanting environment we went there one April vacation and it was a great decsion. Our destination was Rudesheim Germany and Rothenburg ob der Tauber (there are 2 Rothenburgs in Germany). We flew into Frankfurt, staying overnight in Frankfurt and the next morning rented a car (easy) and drove 1 1/2 hours west to Rudesheim and later in the week drove 3 hours south to Rothenburg https://www.tripadvisor.com/Tourism-g187319-Rothenburg_Middle_Franconia_Franconia_Bavaria-Vacations.html.
The area is a bit fairy tale like at any age. Rick's book was a tremendous source of this entire vacation but there is much more to do in the area. Rudesheim is on the Rhine and a scenic, lively small town. There are lots of castles in that area. Although my kids are good travelers and are curious, they were not going to be enthralled by a 15 century tapestry hanging on a castle wall....or not for long. Per Rick's book, a few miles north or Rudesheim, along the Rhine, is Rheinfels Castle...an enormous giant ruin, there is no roof, just walls--perfect for the imagination of kids and interesting for adults. https://www.st-goar.de/en/rheinfels-castle/
In Rudesheim, you can take a terrific short, easy hike up a "hill" to the sister statue of the Statue of Liberty ("Niederwalddenkmal Monument") with a terrific view, then walk over to a gondola ride with more spectacular scenery, get off the gondola, walk through a forest, feed some animals at a petting zoo, then take the gondola back down to a true fairy town village of Assmannhausen, then take a quick ferry ride on the Rhein back to Rudesheim. We really enjoyed this area. Note: Rudesheim has a train track along the Rhine and trains (loud trains) go by constantly. I don't know how the people who stay in the charming hotels along the river can stand it. We stayed at Ruedesheimer Hof in a great family room, 5-6 blocks from the tracks, quiet, and with a full breakfast: https://www.tripadvisor.com/Hotel_Review-g187345-d239085-Reviews-Rudesheimer_Hof-Ruedesheim_am_Rhein_Hesse.html. Here is a terrific source of info on things to do: https://theculturetrip.com/europe/germany/articles/the-top-10-things-to-do-and-see-in-rudesheim-am-rhein/
As far as Rothenberg ob der Tauber goes it is a total fairy tale, it is very popular/touristy, and you need to book in advance. You may prefer other towns in the area but with kids, I thought this was a safe choice https://www.tripadvisor.com/Tourism-g187319-Rothenburg_Middle_Franconia_Franconia_Bavaria-Vacations.html. We stayed in a large family room w/great breakfast at one of Rick's recommendations: Hotel Gerberhaus. https://www.tripadvisor.com/Hotel_Review-g187319-d269259-Reviews-Hotel_Gerberhaus-Rothenburg_Middle_Franconia_Franconia_Bavaria.html. If you go, you MUST go on the entertaining "Night Tour", highly recommended by every tour book, your kids will love it and so will you. If you happen to be in Rothenberg at Easter, there is an unbelievable Easter Egg hunt open to all in the main park "Burggarten" (castle park)...behind a thick castle door.....in a huge park....the kids hunt for gold chocolate rabbits by Lindt...big ones...HUNDREDS of chocolate bunnies are hidden...and found. It is one of the kids best travel memories. https://www.tripadvisor.com/ShowUserReviews-g187319-d1898222-r115920223-Burggarten-Rothenburg_Middle_Franconia_Franconia_Bavaria.html If not, the park is a fun place for active kids, although no soccer area, but if they are up to picking up some sticks and having a sword fight, the park will not disappoint.
Sorry to go on and on but this was a great vacation!