I also have started seeing a child with the same diagnosis but is 9 years old. For receptive language I use a puppet and ask for certain pictures from a choice of 3 (varies depending on his familioarity of category. If he chooses the right picture he gets to feed the puppet with it (making eating noises and making it fun) if he chooses the wrong picture the puppet won't eat the picture and will keep his mouth shut. I also integrate his sensory needs for e.g. he really likes spinning - so I will get him to put a piece of the potato head maybe even 2 pieces before I spin him on a special spinning chair (bough from ikea for kids).