My teaching partner and I use Lego Robotics. She uses the WeDo kits with little people, and the blue boxes (9686) with slightly older little people. They are both terrific for teaching the simple machines, following build instructions, and finding all of the little parts that are all over the floor.
I use the Mindstorms in 5th grade for beginning drag-n-drop programming. I have used Damien Kee's Classroom Activities for the Busy Teacher lessons in the past but I think I can do better creating lessons that would be more engaging with a story that is closer to what is actually happening on Mars.
Two summers ago, I wrote an adventure story on iBooks Author that went along with building various robots from the Mindstorm box and coding it to accomplish different tasks on Mars. (Read the story. Toward the end of the chapter, you write your own ending by going on a mission with your robot.) Then I found out that 5th graders don't actually have their own iPads -- just iPads they can use in the classroom. I'll post the story. Maybe one of you can use it.
The best thing I ever did for my robotics teaching was to create a mini-inventory for the first build. Before students begin the robotics unit, they have to take inventory in their Mindstorm box to ensure they can complete the first build (the one shown in this picture). My inventory list does that nicely.
And here's something else you might need. You know that little red piece that connects the brick to the rest of the first assembly? It's the one that you HAVE to have to make that first build? (And, consequently, it's the one that gets lost most frequently.) Here's an STL file for you to print some extras from your 3D printer.