Need Monetization Ideas For Living On A Marina

Dad owns a marina. I'm approaching the age of 20 and I want to take a small break from online stuff and start monetizing this gold mine. So basically we are the largest freshwater marina in Canada, which means we have a lot of customers. There are 2 offices:
-Main Office: Where everyone pays for yearly docks and buys boats, etc
-Gas Bar: Self explanatory... gas, snacks, drinks

Right now, I am just thinking about the gas bar. I have all winter to prepare as the season is just ending. I cannot really offer any boat related services to the customers because that market is pretty saturated by my dad already (parts, maintenance, sales, cleaning, etc). On the average sunny weekend, there's hundreds of customers a day, spending hundreds of dollar each, and the best part: Most boaters own businesses!

My first idea that I want to try is leaving web design business cards in the gas bar.

There are so many possibilities. I can go around in a golf cart (btw, I got all the capital funds I ever needed) and sell ice and chips, but that's not very expandable, just an example.

What would you do if you had access to thousands of wealthy people? Hundreds of them being millionaires.

I would really appreciate some ideas. Note: The "selling food" idea is taken, as we already have contracts with onsite people.

Wait!
I almost forgot, I also have access to another HUGE traffic source. On the other side of my house, we are at the end of a road. It's a turn around and parking lot. Branching off the parking lot, we have a restaurant, and Sea Doo rentals (there is a sea doo rental contract too, so i cannot do that) and on the weekend, there are thousands of people that turn around here. We have lots of those mobile signs where you change the letters on them by hand and can tow it behind the truck as the sign has wheels. The majority of these people are tourists.

I bought the {city}cottagerentals.ca (as its in Canada) domain. I could advertise that on a sign, and then turn that site into a classified site. The only cost I have on that business idea is web hosting which is a dime a dozen.

I have until May long weekend to get everything setup and ready to rock. Please let me know if you have ideas. I may make a post in the JV section after this. This is going to be hard to come up with ideas as my dad is a great business man and there isn't much room left in the boating niche to offer, just read the posts below to find out the difficulty.

EDIT: Not interested in providing Internet.