It's definitely important at times to turn away business. And, to put it bluntly, business is about profit, not revenue. That said, in the middle of lower economic times, it's not always the right time to turn away dollars.
There are several things to ask yourself before you make your decision. For instance, how much profit do you get from the tents and trailers? How much profit from the cabins? You may find the tents are lower in revenue, but still good profit.
Next, look at the quality of the customer. Maybe the cabin customers pay on time and come back more often. Maybe the tent customers are trouble makers. Remember, it's your business and you get to choose who you want to do business with.
Overall, be careful and make sure the economy is not the reason they're in tents rather than just wanting to be in the tents.