I have a very fearful five year old--he is very afraid of new situations, which is weird, since he is this loud, outgoing, super-friendly kid. And, we lived in WA state for quite a while, while our family was in the midwest, meaning our kids never did nights away with any relatives without us. Now that we are back in MN, I really wanted my boys to be ok with staying away from us, if for no other reason than if we should HAVE to, they wouldn't have the double whammy of whatever crisis came up PLUS staying away from mom and dad. So I tend to think you should encourage the nights away. Your girls are old enough to tell time; do they know when you're returning? Maybe having grandma or grandpa stay at YOUR house while you get away would transition them a little more easily? My son needs to know what to expect, and not knowing makes him VERY anxious. We prepared him for months to spend four days with grandma and grandpa on their farm. He also liked knowing he was going with his baby brother. Maybe telling the girls where you'll be when they're there would help? Planning a phone call? Talking about all the fun they'll have (when my son starts fretting about being away from us, all I have to do is look at him sternly and say, "Now, daddy and I will be gone, so don't have ALL the fun with ...grandma... ..aunt...babysitter..." and he looks at me mischieviously and laughs, saying, "We're gonna have ALL the fun!" and then he's suddenly fine, realizing that he WILL have fun without us--all on his own. Hmmm...don't know if any of this is great advice, but I'd just take it really slowly--maybe an afternoon at grandma and grandpa's? Then an evening? Then an overnight? I'd work hard with grandma and grandpa, esp since they're relatively close, to get the girls out and about a little more, because I think you're right--they are old enough to be alone for a night with someone they trust, and they should be able to enjoy it. I also think, though, that forcing it could backfire--so it's matter of walking that thin line! Good luck!