Picky eater "yucky"

[ebhappydc]

I have a 3.5 hr old dcb who eats absolutely nothing for the 9 hrs he is here many days per week/month. His parents and I know he has always had trouble with textures and is a very picky eater (although cookies, cheerios, chocolate cake, and pizza seem to work fine...) He is seeing a nutritionist to help him get used to better foods choices, but I don't see improvement.... he's growing fine, and not underweight. he will eat bananas/yogurt, but we're not always having those every day and if I give to him then all the kids want same.
I was starting to worry about blood sugar levels and energy because on the days he chooses to eat nothing, he does tend to lie on the rug a lot by the end of the day. So I tried giving him Cheerios when the others went down for quiet time because somehow it made me feel better that he had something in his tummy, but now he has started to announce at lunchtime to his friends that he's going to wait til he gets his Cheerios when everyone's asleep..... Do we have to worry about fainting/sugar levels etc if they're only drinking water for the day, or is staying hydrated for 9 hrs enough at this age? I always let his parents know when he hasn't eaten so they should at least expect him to eat at dinner. They are great parents but don't know what to do either. Water enough for the day? Tx!!