Hi T.,
I guess you could ask that any houses with older brothers send the boys away for the night when your daughter sleeps over. LOL I'm sorry, but that is a little over the top.
If you know the family, have spent time with the parents, and share core values I think your list of rules is fine. Remember that what we teach our children is still in their head even when they are not with us and 6th grade is old enough to call you if she feels uncomfortable and wants to be picked up.
I tend to host more sleepovers than have my son spend the night elsewhere. But I think that came about because his friends prefer to be at my house rather than their own. So that's another way to go with this - become the house that all your daughter's friends want to hang out at.
Trust me, there will be times she will ask to stay over a friends house and you will just know that the answer is "No". Stay involved in her life, school, extracurricular activities in order to get to know the parents of her friends. Let her know the expectations when she is sleeping at a friends and have an open talk with the host parents about what you expect.
It will be fine - sleepovers are a childhood rite of passage.