I've often taken mine away solo since they were babies. Anything from camping on a very basic site, holiday park to nice hotel.
There is the boredom of being the only adult but for me it's outweighed by the need for an adventure and breaking up the school holidays. Can you take something like a laptop & small speaker with loads of media or dvds? Whilst it's nice if they come in at 9pm exhausted, a programme after dinner, or to keep them happy on a rainy morning is great. Last summer touring Europe we ploughed through Falling Skies again at night time, it was really nice.
I like downloading podcasts to play as background noise sometimes. There's some good radio 4 ones that are fine for younger ones to overhear and appreciate on whatever level they want to.
Just a minute, Unbelievable Truth, Infinite Monkey Cage, No Such Thing as a Fish, Museum of Curiosity, History of the World in 100 Objects, More or Less, Cabin Fever, Another Case of Milton Jones. Some you have to buy through somewhere like Audible but it's worth stocking up. Horrible History audio books are ok too.
When you're driving make sure they have a few things to hand to reduce distractions. Water, snacks, bag for rubbish, small towel for spillage or vomiting 