Whether the birthday boy or girl is turning 5 or 50, a birthday party with a large number of attendees has its own challenges. From keeping the guests entertained to feeding them to even keeping track of everyone there, having some specific plans will give the party a higher chance of success.
Capture the Flag
The game Capture the Flag is made for large groups and is suitable for most ages, from kids through adults. Choose a large area such as a public park to host the game, and split the guests into two teams, each marked by a different color. Give everyone a bandanna in the color of their team so that the team members are easily distinguishable. Make sure to have an indoor option planned as well in case the weather is unexpectedly foul.
A movie night, either inside if you have the space or outside, keeps your guests occupied and entertained for a long stretch of the party and gives them a common topic of conversation afterward so that the guests who don't know each other can have an easier time mingling. If you do the movie outside, use a projector and play it in the evening. Let your guests sit on blankets, and take care that the taller ones do not sit too close to the front.
At its most basic, for a dance birthday party all you need to do is string some lights in a backyard, put out a punch bowl and fire up a playlist preset to dance-worthy music. Renting or borrowing some good speakers if you don't already own a set can help the ambiance. Give the shier partygoers something to do by setting up a couple of games on a patio, if you want.
Serve foods that can be made both in bulk and in advance. For the cake, you could always do the traditional sheet cake, but using cupcakes instead will make it easier to have the right amount for the party and make it easier to serve with minimal effort and time. Have a buffet line for people to arrange their own plates instead of serving everyone yourself.