Ooo, this is cute for above the desk (too bad they don't tell you how to make it, but I can figure it out!). But talks about how to make and prep chalkboard paint. Thought magnetic paint sounds disappointing.
DIY: Reuse a large frame and a piece of sheet metal to make a chalkboard. Mount it low on the wall for easy kid access. Also hang some painted galvanized buckets filled with calk. Toss in some floor pillows.