You might consider changing your cover charge to incorporate something for the food as well. I've been to belly dance shows who did this in restaurants, and they worked with the owners to allocate $15 per person for food and then added whatever on top of that they wanted to cover the entertainment. People were then offered their choice of 2 or 3 different meals that could be provided for that price. Of course, depending on your local economy, you could charge a different amount.

Another option is that when people come in the door, your cover charge includes some sort of minimum drink order. For example, let's say the place charges $4 for a glass of wine. You might add $8 to your cover charge for this, and then give the person 2 drink tickets which can be redeemed ON THAT DATE for glasses of either beer, wine, or soft drinks. They don't have to redeem them if they don't want to, of course, but either way you've got $8 per person that goes to the restaurant.

It is a fact of life that many people assume that just showing up is supporting the dancers (or the musicians, or whoever is performing). Well, it would be if you were dancing in a park! But otherwise, If you don't charge a cover of some type many people will get a glass of water or soda and sit at the best tables for the entire show. In their mind, they were invited to watch a show, not to purchase a meal, no matter how you advertise it!

If you want to include food or drink in your cover charge then find out what your venue is used to serving at that time of night and include that. If your cover includes food the venue needs to be prepared to deal with lots of meal orders, and they may not be able to pull it off if they are a cafe that usually serve a lot of drinks at that time. Delays of one hour for a sandwich and tea with no water on the table won't thrill your guests. And the cover has to be collected in an organized way, either on the tab or at the door by someone dedicated to the task. And if the venue insists on seating guests who 'didn't come for the show' (and therefore don't have to pay a cover) - well, believe me, your guests will figure this out for the next time.

Ask me how I know this :) No, seriously, it's not just a belly dance problem. A local caffe owner tried very hard to provide great entertainment of all kinds with no cover or minimum during what is known as Trolly Hop weekends and ended up with entire tables of ladies who would take the trolley to his door, come in, sit down, order a tea or a soda or a water, and sit there for THREE HOURS while possibly-paying customers lined up outside the door.. He attempted properous thoughts and a generous attitude for a year. Now he charges a cover. :) Another time we went to a gig organized by a very well-known, well-liked and experienced dancer and organizer and met her outside during break in tears because people were coming in, not ordering anything and the restaurant owner was furious. I've talked to restaurant owners who discovered that people dealt with an open-ended requirement (no minimum) to purchase food by splitting a salad three ways and calling for lots of extra (free) bread to go with it.

So ignore people's desire to get great dancing for free and charge the cover that works for you! IMO.