Hello @Helen3603
No guests won't be able to book for 4 on your listing because it's set up for a max occupancy of 2 so it's only when guest read your full description that they will discover that they can bring extra 2 people.
There is a lot to read in your description so guests won't see this immediately and there seems to be general consensus that guests don't like reading descriptions and prefer looking at the photos so it is something that they might miss. The fact that you have added the air mattress in the "Where you'll sleep" section is great and guests see that easily.
An idea would be to see if you can reduce the amount to read as some information is already available elsewhere. I am a fan of using a varied array of pinpoints to highlight what my listing offers so that guests can see quickly what my place includes.
Recommend that you use the preview feature that we have in host mode to see our listing as a guest. As it stands, a guest cannot enter more than 2 people for your listing so it won't come up in a search if a guests put in 4 guests.
You'll have to use the request money feature I think to get the extra fee for the air mattress that you can do once the reservation is confirmed plus any city taxes that may be involved for having additional guests?