Play dates, Strangers, and other Such Things

I would consider myself a cautious parent, perhaps a tad overprotective. I obviously want my kids to experience things on their own but I also want to ensure that my children are safe and I am not doing anything that could put them into harm's way. An issue that has come up a lot since our daughter has started school is 'after school play dates.'

Prior to this year "play dates" meant either going over to my sister's house so she could play with her cousins, her cousins coming here or getting together with friends I have known for years. She has made some great friends at school and I have little reason to believe any of their parents would wish any harm to befall my child. However, I don't know them. I know that different parents have different philosophies and what might be allowed in their home might not be allowed in ours and vice versa. Our general rule has been, since quite a few of her school friends live in our particular neighborhood, that they can play outside in front of houses, but not in each other's homes. This has worked out well as the few girls she plays with have parents with similar philosophies.

Lately though I have had repeated offers from one of the girl's family members (not her mother, but another member who watches this little girl after school) to have our daughter come over and play. Truthfully I am not comfortable with this at all. They live close to us, but not in our neighborhood and the little interaction I have had with the mother and her husband was uncomfortable enough to give me pause. This family member asked me a week or so ago if my daughter could come over. I explained to her that our general rule was to not allow play dates unless either myself or my husband went as well. She seemed okay with this, however this would also require that I take my son and other daughter over as well, which I don't want to presume is okay with them and frankly, and this sounds bad, but it's more hassle than it's probably worth.

So, any advice on how to handle this? I don't mind going over a couple of times and truthfully if I had a better feeling about the girl's mother and step-father I would not be as nervous about this but we have very different ideas about what is appropriate, etc.