Hi :)
We have traveled without kids for about 5 days total, but were always able to get back ASAP - which is my requirement. I could not go anywhere that was too remote to get back in a pinch.
Usually we have just gone for a long weekend getaway - either with friends or just the two of us to reconnect. It really is worth it. When we can't get away for extended periods, we go for a night to an inn that we can drive to. Even a night away, with a meal, and a nice breakfast/brunch the next day and a little sight seeing is awesome.
It really depends who you have to look after your kids. We've had family come here and look after them which worked out the best for us. The kids' routines were not changed very much, and I was able to have as much prepared ahead of time to help out the grandparents and keep it consistent.
It is a bit of a challenge for older people. So having meals prepared and even clothing laid out by day (especially if there's a gym day or uniforms required) helps out. I don't want my mother or MIL wondering what they should do - it's too stressful for them. It's much easier if you have it fool proof for them. That way they can just relax at least part of the time and enjoying visiting with the grandkids.
I babysat a lot as a teenager and early 20's for families for long weekends, etc. And I had my mother as backup. If you do go that route, make sure the sitter's parent is available in an emergency. I was trained for emergencies (had worked at daycares and summer camps) - even so teenagers can become overwhelmed. Knowing my mother was a quick call away and she could be there in a few minutes made me and the parents feel a lot more secure.
My brother and wife left their babies with my mother and went to Europe. They had a great time. My mother I know couldn't relax the whole time they were gone. She kept it to herself but I could tell. If anything happened to the babies, she knew she would have to make decisions before they would be able to get back in time. That's quite an expectation to put on someone so make sure that's something they can handle. My mother was prepared to do that, but it's something to consider.
If you feel confident in who you leave them with - it's a wonderful opportunity to have some alone time away from all the hassles of home :)