Family Vacation in March teen daughter wants to take boyfriend along.....

I am planning a Spring Break Vacation with my siblings and their kids.I have no problem with the BFcoming along. But as I was trying to figure out the exact number of bedrooms needed she suggested that her BF sleep in her room..I said no way you two aren't married and I just can't see myself allowing this. My husband says no way also. He said that if we weren't married his Mother wouldn't allow us to sleep together in her prescence and we have been adults for many years. Do you think we are being too old fashioned? I know kids are allowed to do way more than we used to in our day. But would this be going too far?? Forgot to add she is 18 and in the 12th grade and so is the BF. I suggested that he use the pull out queen sofa sleeper that is available...is that fair?