I would wait for a few days and try it again. I can choose special meals on my domestic flights and child is an option so I think you should. I wouldn’t really worry the doco deserts on the standard meal is great and which child would refuse 3x of that!!! Don’t forget if it’s an afternoon flight then it’s finger sandwich and scones again all kids loves those things.
I would recommend to check in the forum about CE meals before you call.