UH, I don't have any great advice re how to get your ds to try more foods (other than seeking out a sensory OT for suggestions)... but just wanted to add one thing to the suggestions already offered up - sometimes young children refuse certain foods because they cause them actual pain/discomfort/etc when they eat them - this happens sometimes with kids with food allergies - they will refuse to eat a food and the parent thinks it's just a kid being a picky eater, when really what's happening is they have eaten that food at some point and it made them feel sick.
I am not trying to say that's what's up with your ds, but just wanted folks to be aware if they are seeing picky-eater behavior and also seeing other symptoms (random hives, stomachaches, flushed cheeks) then it might be worth paying close attention to the types of foods they are refusing to eat.
Best wishes,
polarbear
