We live in the USA and I have kept in touch vaguely with a number of friends across the world through Facebook over the years. One of them, a really lovely person but who I'm not particularly close to (we shared an office in Paris for a year in 2001/2 and haven't seen each other since, we message about twice a year) is coming to the USA next summer and has messaged me and asked if she and her husband and kids (none of whom I've ever met) can stay for a week. I'm not keen on having visitors apart from family to stay, we have a large dog who can be unpredictable with people she doesn't know in her house (so would have to go to the dog sitters) and although she is really kind and lovely, I just don't know her well enough to have her stay. Aibu and how can I say no?