Hi @John1995,
Unfortunately what you want, is currently not possible on Airbnb!
The only thing you can do, is making it very clear everywhere in your listing (Title, Body and House-rules) you can only host maximum 2 adults and 2 children.
This will not disallow, 4 adults to book you. But it is about all you can do, to prevent this.
You can also show, the bedding configuration in your listing (just have a look at my listing).
When more than 2 adults request to book, you can always get in touch with Airbnb. And claim these guests do intend to break your house-rules. And have Airbnb cancel them.