This is Labor Day weekend so it could be less than 45 people that will be served but please prepare food for at least 40 people.
You're welcome to only cook and not serve, but if so, please make a note so that we'll request for servers. They generally ask for no more than 4 servers as space is tight.
Kids as young as 3 are ok to pass out water to people who come. I don't think the people are "scary" but then it is the public who would come get lunch. Please use your judgement as a parent. I have had my 7 and 9 year old come help serve food. My 7 year old can pass plates of food or also put food on plates as helper too.