My 3yr old son who has spina bifida broke out with small red bumps all over his skin and he is not itching what can that be?

Heat or viral. Small red bums could be heat rash. Might be a virus or if he has been exposed to a new soap, detergent, or food might be a slight reaction. Rashes are best diagnosed when seen. If it persists or worsens see your pediatrician.
Rash. A rash can have many causes: 1) recent environmental exposure (usually itchy though) 2) recent viral infection (like a cold or diarrhea) may then also have associated non-itchy bumpy rash 3) medications can cause rashes.
See a doc. Could be any number of things. Allergy, infection, rash due to foods, medications etc. I do not think it is necessarily related to spina bifida. You should take him in to see his pediatrician.