My son had internal head gear. Called a Herbst Device. He drooled a little at first. It goes away in a matter of days. They get accustomed to it. I read all sorts of horror stories about herbst devices and drooling kids, but my son adjusted just fine without any sort of major drama. He drank milkshake smoothies for a day or three, then soft pastas and baked potatoes, soft chicken, boiled eggs, etc. Then he was able to eat normally, pretty much whatever he wanted (that is allowed with braces rules--no meat off the bone, no chicken wings, no popcorn/peanuts, no jerky, no sticky candy).
If you have concerns, always talk to the treating doctor. But try not to blow it up into major drama. It's unnecessary and creates more emotional distress for your kiddo. Acknowledge his issues (pain/awkwardness/difficulty eating), double check with the ortho, and then be matter of fact about getting through it, or having adjustments made if that is necessary.