What you have described may be his epiglottis. It can be seen in young children when they yawn, cough or open widely.
I've never seen or heard of an "extra tongue" in any craniofacial or genetic disorder.
I suggest you take him to a Craniofacial Center if possible. They are usually located within a large hospital. The other consultation would be with a Speech Pathologist. They are well trained on evaluating not only his speech but swallowing and throat muscle function.
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