To preface, we have visited Crest Hollow and are interested there, and we're going to be visiting some of the shuls, including Sephardic Temple, Shelter Rock Jewish Center, and Great Neck Synagogue. The venue doesn't have to do only kosher things (c.f. Crest Hollow), but we need kosher food available. We're trying to keep the budget for the hall and food to $100pp or less, before service and tax, which most if not all of the above will do.
If anyone knows of any other places (we're thinking of a wedding size of 250-300), please let us know!