[Company's name] is pleased to announce a business gathering at [location] on [date]. The festivities will begin at [time] and will end at [time]. You do not need to bring anything to this party; the company is fully funding the occasion. Each employee is allowed to bring one adult guest.
Please contact [Name] to confirm that you will attend the function and to inform him whether you will bring a guest. We look forward to this time of fun and food, and we hope you will attend.
Very truly yours,