Not all places will serve alcohol. Some churches will offer their auxilary kitchen staff at low costs. Provide special events to enhance the experience. Using someone's large house with swimming pool may actually intimidate or offend some classmates. On Saturday you could arrange to tour the high school and then have an afternoon pot-luck picnic that allows classmates to bring their children.
Local classmates can bring the food, others can bring the drinks and chips.
Be sure to reserve space early to get shelter and cooking grills etc. Try to provide activities for the younger children. Have an official greeter to help with introductions of guests get people into the spirit early. Provide nametags at all events. You must plan the evenings events and then provide a printed program with the events and class roster.