Fascinating question, Bob Lima.
As I think through seasonality like you describe, I actually think the down time would be a great time to plan out implementation/execution.
During the high season, when you are working with clients and operating tours more regularly, I bet you come up with lots of great ideas on how to be better and more efficient. You also probably have lots of conversations with customers. Those conversations likely give you ideas about what other kinds of clients might enjoy the work you do. But you are also probably running around like mad making sure your current customers have the best service possible, and are putting out a lot of fires.
One suggestion is to keep a running list or capture in some way all the great ideas that come up during the high season (I’d call that the visionary work).
Then during the down season, you have time to sort through everything, prioritize and weigh what ideas are truly great and what ideas would impact your business on a smaller scale. Do some analytics around each one. And figure out the steps to implement the great ones during the next high season. Or use them to bring in more clients.
Given my limited understanding of your business, I hope that is helpful!