You may be right. The owner of the theater encouraged me to promote the screening everywhere. I had posters made we later re-used at NY Comic Con. I think I listed a previous screening party under promotion. I forget the year the previous party was held. But, promotion sounds right.
If all that showed up are cast and crew with their friends and family, a screening party can also be considered a "company party" where meals and entertainment is 100% deductible.