Outdoor Party

Hello, my mom and I are planning to celebrate her 50th b-day which was back in march but she wanted an outdoor party; we are having her co-workers,family and friends,over 100 people.
She has decided to have everything purple and yellow, bright colors representing summer simce is going to be held in june, my question is about the food how can we know we have the right amount and proper o`doevours, meal, cocktail etc, our background is latin so if you have any suggestions of how to get started please reply, thanks.