@Sara1152,
I saw their is not much difference in price for the 1 or 2 bedroom listing. If you offer the entire guesthouse, you could decide to make 1 listing and set up a base price for up to two guests and set a fee for the additional guests:
https://www.airbnb.com/help/article/1507/how-do-i-add-a-fee-for-additional-guests-to-my-listing
That still does not solve the problem of closing 1 bedroom (As it is the entire guesthouse offered, which offcourse includes two bedrooms)
But if booking is for two guests and they are willing to share 1 bedroom (which will be most common, i guess) you could offer a discount, to be mentioned in the listing. Condition is also then the other bedroom will not be accessable. The discount can be provided by special offer.
Otherwise you will have to offer bedrooms instead of entire guesthouse and link the calenders. Advantage then is you can make reservations to different guests in same period.
Best regards,
Emiel