probably something you'll need to address in the morning - lest you want something disturbing burnt onto you retinas! i think pointing out that a decent introduction, several meals or something and an assurance she won't be ripping off the family silver is acceptable. oh...and you may want to point out that yours definately isn't the local knocking shop!
my son did this with his girlfriend of three months (they were both 16 at the time), so I had words with the pair of them in the morning, dragged them both to the local GUM clinic (well, someone had to!) and said if they made me a grandma at 32, i would be less than impressed. they are still together (over two years later), she is very respectful and they don't rub our faces in whatever it is they do in his bedroom for extended periods of time.
you have to be honest about what is bothering you and be reasonable that, like you, he obviously wants a bit of how's your father now and then! also, he has to understand that it is your house - your sancuary, actually - and you all have a right to feel comfortable about things. also, we ladies do like a bit of notice when people come round in order to be tidy, have enough food in the house and can fit things in with everything else we end up organising. good luck...you'll probably need it as it can be toe-curlingly embarrassing, but will be necessary for a happy household x