My sister and I rented lakeside cabins in New England for a fall getaway. The idea was that the families would spend a long weekend together, share meals, do all sorts of outdoor activities and let the cousins bond. As it ended up, I had her kids for three solid days--took them fishing, hiking, apple picking, horseback riding, fed them and had them sleep in my cabin. My sister and her husband spent the week on their deck reading. And she had the nerve to say at the end of the week, "Bill and I haven't had any quality time together. It's been a bit of a disappointment." It took all of my self control not to toss her in the lake.
Congratulations on your self control; this is a true hallmark of a Grace. And, given the laziness she seems to have demonstrated, you would have had to fish Sis out of the lake, lest she expend any energy to swim ashore.
Here's my take: you basically achieved your goal. You hoped to do outdoor activities with your kids and have them spend time with their cousins. Sure, the vacation fell short in your estimation since you served as camp counselor, babysitter, fish hook baiter, activities planner, chief cook and bottlewasher, while your sister sat with her feet up relaxing. But, your kids probably had a blast, your nieces and nephews probably had a terrific time--much better than they would have if left to the devices of their own sedentary parents--and you learned a lesson about traveling with Sis. Next time make it a day trip, or consider taking her kids and leaving her home. I suspect her conduct would have been far less egregious if you weren't staring at her repose whilst you consulted trail maps and scaled the trout.
One more thought--there would have been nothing wrong with sending Sis's kids home after a morning (or day and a half) at your house. Doubtless you wanted to maximize your kids' fun with cousins, but martyrdom does not become anyone, least of all a Grace.
For an amusing portrayal of familial cohabitation on an alleged vacation, watch the following.....hopefully your long weekend did not rival this: