Music (classical calms and interests them), visual stimulation (children's museums, art events, crayons/coloring books, craft classes), anything like a playground that has motion or things to move in them (I even took my two to swimming lessons at that age -- just have to be more aware of where they are at all times), and ... a very cheap digital camera that you can show him how to turn on, and then teach him how to take a picture with. Tell him that when he sees something he likes, to take a picture of it. Then download the pictures and see what he is seeing. I also bought a bicycle trailer (with canopy/rain fly) that toddlers can be belted in (put a helmet on my Asperger's child -- An Autism Spectrum Disorder), and just bicycle down a nature trail. The kids love the motion, and the camera in their hands (make sure you belt its handle into the trailer too), then just go forward.
An Older single mom who raised TWO disabled Kids on her own -- one has Severe ADHD and the other has Asperger's Syndrome (High Functioning Autism).