Unfortunately, there's very little for younger kids about the Thirty Years' War that's engaging, in my opinion! But three quick ideas as you prepare for next week's history topic:
1) Consider acting out the war with Legos. This home video is a little dry in my estimation, but it may give your kids an idea on how to do it themselves. Army men may also work!
2) If you have multiple children, have them stage a drama. You might put signs around their necks to designate sides or main characters; have a "Treaty of Westphalia" paper that both sides sign. (For older kids, have them make the signs and papers themselves as another way to remember who were the sides, what was the treaty, etc.) They can designate parts of a room--or different rooms--as different countries, etc. You can be as elaborate as you want. I'm sure my boys will be involving the Nerf swords.
3) I thought this digital poster explaining the Thirty Years' War was pretty cool!
Note: You can apparently create your own on Glogster. Here was the original blogpost on creating the poster by a homeschooler. Glogster "is the leading global education platform for the creative expression of knowledge and skills in the classroom and beyond. We empower educators and students with the technology to create GLOGS - online multimedia posters - with text, photos, videos, graphics, sounds, drawings, data attachments and more." Kind of a fun way to put together information--may have to try this out!