I am also in a resort market with about 10K resident population. I have been doing business here for 10 years.
Advertising in the slow season is what I call “shouting into a well”.
My advice is to concentrate on controlling costs.
Marketing activities that do work for me at those times of year and make some kind of economic sense:
Get into the local coupon book. Use what I call a “try-me” offer. The goal is not so much profitable sales as it is to get the locals to try you for the first time. Our offer is a 16" pie with up to five toppings for $14.
Get the list of special events from the local Chamber of Commerce. Sponsor any local business event by providing 20 free pizzas on the condition that YOU get to serve them and interact with the other business people. DO NOT DONATE PLAIN CHEESE OR PEPPERONI! This is your chance to shine, donate the best, most interesting combos on your menu.
Join a local service club like Rotary. If you are like me, you will enjoy it anyway. It will cost you about $1000 per year (and some time) to be a member and will return more than any other $1000 you spend.
It is OK to trim back your hours, but stay consistent as far as what days and hours you are open once you trim. Make sure service and quality are great.