My sisters and I are planning our first cruise (Yeah). I have one question there is a talk about how small the cabin's are. Can you book 3 people in one room? I don't know what the limits are but I don't think any of us want our own room we would rather share. But at the end of the trip you can ask me if I want to share ever again. ha
I think the main problem you 3 may have is sharing the one bathroom, but the cabin should have enough room to sleep and hopefully drawer/closet space. You can store the luggage under the beds and if for some reason it doesn't fit, just ask your cabin attandant to store it for you.
Also strategize your "getting ready" time when the bathroom and cabin space seems to shrink. Might also suggest kicking the room temp down before nights you dress up. I've been in a cabin with 3 other guys and I know it can be done.
I put my three teens in a room and they are ok with it. If you can swing it, go for the minisuite or an outside room with a balcony for a little extra room. Rates for a third person are usually much lower, split the cabin total three ways and maybe you can go a little bigger. Consider it a bonding experience.