birthday party after school?

I’m not to great with planning parties and the location (pavilion at park) i would like to have both kids birthday is booked for the weekend. I have a Friday slot that is available but with school still going i’m afraid no kids will show up. What times are best to have a birthday party? Kids will be turning 1 & 5, and school around here let’s out from 2-330 and the day care closes at 6.