You aren't allowed to bring food or drink into the park, so whatever you want to eat has to be bought there. We were there between 10 and 11:30, so we didn't buy anything to eat. I did note that there were several places to eat including the Banquet Hall, a rental hall for groups.
Pictures are of the Mermaid Galley Restaurant entrance with a peacock who hopped up onto the cigarette disposer to pose plus two from a greater distance with the peacock's tail unfurled, the Captain's Quarters which is right by the underwater theatre, and the Sweet Stop and Shop which is a gift shop and snack shop by the entrance.
There are also two places to get food over in the water park (closed when we were there because it was January and COLD) called Pirate's Grum and Snack Shack.
For a taste of what's inherently charming about Weeki Wachee, have lunch at the Nellie's restaurant. The restaurant serves classic favorites - New York steak, cottage pie, grouper etc.
This is a good place to drink a pitcher of beer and munch on buffalo (chicken) wings or deep fried fish smothered in tartar sauce. The balcony view of the park is great, as this photo shows.