How much room do you need for a pow wow?

Next year on Memorial Day weekend, my brother is having one at his place. The yard measures 300x150 feet. He and I have remote control trucks that we drag race. He has an in-ground pool that we'll play Marco Polo in. We are inviting almost 100 guests. The music will be provided by me bringing my laptop hooked up to one of those All-Tech Lansing bassy speakers with the volume turned up real loud. We'll have a nice picnic and the kids will be entertained by some inflatable fun houses as well as the pool and some of the back yard games like bean bag toss, croquet and more. So is my brother's big enough for this fun day?