adding on to Pond & Stream for a 4th grader

I’m planning on doing the Pond & Stream study this fall with a K’er, 2nd grader, and 4th grader.  Should I add something on to it for the 4th grader, and if so, any suggestions?  I did not order any of the optional 3rd grade books as he is dyslexic and I would likely have to read them to him which probably isn’t going to happen.