My son does this too. Sometimes he doesn't trust the food - it is different. I think it is also a problem with the crowd. A lot of times I let him do something else while the whole, big family is eating. When people have moved on a little I'll corner him and get him to eat when it is a little more quiet (sometimes we are sitting on the floor and I'm spoon feeding him). You might try baby steps like a picnic in the living room, then backyard, neighborhood park, etc

I'd agree with Rock here. If he's not compromised, it might not be as big a problem as you think. My nephew had the same issue when he was 4, but now that he's 12, he eats at school. He eats what he brings from home, not a school lunch, but he eats. What I'm saying is, focus on what you can control and hit the food thing lightly. Try bringing his favorite foods/snacks with you in the car, at the park... Desensitize him slowly. In the meantime, the smoothie might help, but don't worry too much about this one. It might work out on its own.

Sometimes Autistics have texture intolerances, like tags on shirts, which John Elder Robinson had, so he cut out the tags. Simple. Some can't tolerate eating the apple, but apple butter and sauce are fine. Locations Eating can be one of those Anxious Producing things, which can be managed by giving choice A or Choice B. Eats @home (A), not at B (Grandma's). Familiar (A) Home, Partially Familiar (B), Grandma's. Try and identify his Comfort, his Control, his Security areas.

Some babies will fall asleep anywhere there Security Blanket is, with the Comforting satin edge, which they Control in their fingers. (98 words)

i had to send a sprite everyday with my son...it worked !!

It took 5 psychologist, all mousing the dots. Finally, an aquaintence suggested the condition, and surprise, a whole set of doors opened, with finall confirmation with the Autism PhD.