While I empathize with the OP. I am afraid I'd have to side with the kennel owners. That issue hits close to home for me. As a nurse who works in public service and with a father who is a Vet who boards animals as well I've seen first hand how "loyal" and "valued" customers can and will take advantage of a business owner or public servant who gives them special treatment. While the OP I'm sure is not one of those types, It only takes one to ruin a good thing. And once you give an inch you often lose a mile.
I live in south LA, my dad offers boarding of animals during hurricanes for people when they evacuate but he has to charge more money than his standard boarding fee during that time. This is b/c while we are under evacuation he has no source of income other than the boarded animals which are generally there more than a week but he and his employees can not evacuate, they must be paid for thier time, animals must be fed/watered cared for, generaters must be run, etc.etc..expenses dont go away with the hurricane. You would not believe some of the things he has been told by "loyal" customers because of his price change and b/c they want special treatment. So I see it from a buisness owners prospective too.
If you had made special arrangments prior to the boarding of your animals then that is one thing, but if not, then in my opinion you can not expect someone to rearrange thier life to accomidate yours b/c you failed to plan ahead regardless of how easy or insignificant you think it may be for them to do so. It falls on you as your responsibility to know and agree to the terms of service provided to you ahead of time and if that service fails to meet those terms then there is an issue. Otherwise the fault is only yours.
That is NUTTS! I mean who's watering, feeding, caring for the dogs over the holiday closed time? Someone better be there...so if "someone" is...why can't you bail your dogs out? I can see if it's a county shelter or something...cuz they want the boarding fees and dog at large fines and all that, but come on...this is a kennel you've used before? I think I'd be shopping for a new place. Ask them who is feeding your dogs while you wait?