Do it, a warning gives you the chance to start medicating pup ahead of time (some recommend taking it a few days before a stressful event) and make sure he’s inside when the noise begins.

I’m not sure how effective it would be on a kennel without a door but you can buy stick on soundproofing foam intended for musicians. Perhaps try it inside an enclosed space like built in wardrobe or a ‘litterbox cabinet’ so there’s a quiet place to hide?