Activities to help with sensory sensitivity and modulation difficulties
related to improving sensory information processing: 

• The key to this is heavy work type exercises, meaning activities in which resistance is used. This to activate the part of the nervous system, which has an organizing capacity.
   
• Massage your child  every day using firm pressure.
  Several times during the day provide him with deep pressure on his shoulders and hips, so he can  cope with changes better
   
  
• Rolling into a comforter or bath towel and trying to get out by pulling yourself out or rolling out against resistance.
   
• Activities using clay or playdough.
   
• Lying prone across from one another: pulling a rope and see who is the strongest: of course, is your son.
   
• Games using pushing and pulling, either with a rope lying prone (as above) or pushing mom/dad or the wall away. Important is that the lower back stays straight
   
• When your child sits on his chair or in the circle, provide him with something heavy on his lap. This can be a beanbag or a weight. It will help in organizing his nervous system not to over- or under react at other times during the day.
   
• Lying prone and supine. A ball is being rolled over the body. Some pressure is provided while the ball is rolled over the body.
   
• Pushing that same ball away while the partner is providing resistance
   
• Lifting buckets of sand, or other heavy objects, such as a pile of books.
   
• In the sand digging a big hole, getting in and covering yourself partly with the sand.
   
• Carrying a somewhat heavier backpack when going for a swim or shopping for groceries
   
• Chewing gum or sipping from a water bottle with a nipple or straw, or chewing carrots, celery sticks and other substances requiring heavy mouth work.
   
• Sitting on a skippyball, bouncing and moving forward.
   
• When performing the above activities, please vary the speed, the rhythm, the speed and the amount of resistance provided, as this will help improve sensory modulation. In other words, it will help your child coping with the amount of variation. This may positively influence his difficulty with changes in routine.

A great book with many more ideas is The Out of Sinc Child has Fun by Barbara Kranovic

Good luck.