I know Jem Caterers is really good. Here is a phone number 516) 867-8030 but not sure if it is the right one. I know they work out of a temple in jericho and the sands in lido but also might do private places as well.
Most Conservative temples, if they have a catering facility, have kosher caterers. You may have pay a fee for the Maschiach to oversee that all is kosher in addition to what you pay per plate as well as gratuity. You may wish to do a search for kosher caterers who cater events that do not have in-house people.
My brother used Jem for his wedding at atlantic beach sands. It was pretty good. When he was in high school my husband used to work for Maizone (sp).
