It is not unusual for a dog who does an excessive amount of barking while kenneled to suffer some laryngitis. Coonhounds are generally a bit high strung and so I suspect the barking continued not only during the day but well into the night as well. He probably didn't get a lot of sleep (hence his lethargy) and may not have eaten very well either.
I would not be surprised if he broke with a bout of "stress colitis"- diarrhea characterized by increased frequency of defecation, straining, and often fresh blood and mucus. If he does, contact your veterinarian for a dose of Pepto Bismol or other anti-diarrheal and feed a bland diet (boiled hamburger or chicken with rice) for a few days.
He is still young and so may eventually adjust to being boarded. But, if possible, it would probably be best if you were able to get a pet sitter or leave him with friends.
If you are not noticing any protracted coughing (usually a dry hacking couch that racks the whole body), then kennel cough is probably not going to be a concern.
