Try putting on a classical music CD or folk music, or children's songs to listen to while he is playing. Write down the details: "Listened to Beethoven Piano Sonatas" or whatever is appropriate. (Painless learning). You could look up a short bio. for kids on the internet, print a photo and attach, put together in a binder for Music.
Write him a one-line (or one word) note. Leave out paper and pen so he can write one back. Don't correct the spelling on the notes. Just enjoy the process of communicating this way.
Read enjoyable stories to him. Point out occasional words in the story that he knows how to read, or can sound out, and have him read them as you go along, without slowing down the story too much.
Let him photograph the toys he is playing with.
Fold a few sheets of paper in half and staple to make a small blank book. Ask him to tell you a story about his toys. Write it down. Illustrate it together, if you like. Read it together. Read it again. Perhaps you could add a photo later when convenient.
Another alternative is to put on a play with the toys. A cardboard box or 3-panel display board makes a good puppet theater. The child can decorate it with crayons, pens, paints.
Come up with math activities involving food or treats. Introduce, review, or practice math concepts with crackers, raisins, nuts, fruit, breakfast cereal. Yum, yum, subtraction is fun.
And, of course, drawing, painting, tracing and various craft projects capture children's interest and teach lots of needed concepts and skills, including pre-writing skills.