Definitions matter. A “twin” sleeping room in Oaxaca City has a different meaning than in Sydney, Australia, New York City or London.
You should have seen the time I had deciphering the room/bed situation when I organized a study abroad group for University of North Carolina at Chapel Hill alumni in London last year. A totally different vocabulary.
During a recent inquiry about booking a room at a nice bed and breakfast, here is the reply we got:
Single room (double bed) with a cost per night $ 900 pesos (2 people).
Double room (king size bed) with a cost per night $1,000 pesos (2 people)·
Twin room (2 double bed) with a cost per night $1,200 pesos (4 people)
We were mystified by the idea that 4 people would share a room with two double beds!
So here is my advice and help to decipher the vocabulary! What matters is specifying the number of beds in a room, not the number of people. So, twin refers to 2 beds, not the size of the bed. You just need to calculate the number of rooms you need with 2 beds and the number of rooms you need with one bed.
Then, order the rooms specifying number of beds in each room and the number of people you want in each room with one person per bed. Let them know that usually there is one bed per traveler unless a couple wants to share a large bed.
You just need to be clear.