We both have full on jobs and often have to do work on holidays. We spent a lot on childcare when dd was young and on the mortgage. Social life was almost non-existent.
For holidays, we have gone to CP a number of times which was surprisingly great. We always planned to go out locally to the site to various things nearby, but parked on arrival and only moved the car again to pack up at the end of a week.
The fact that the site itself was relatively low traffic and lots to do for DCs (plenty of playground stops, swim at least once daily and often twice to wear her out (late afternoon was great as many headed away to get ready for dinner having been there all day), other paid activities available including Kids club for younger and getting into adventures as they get older, restaurants to enjoy 1 meal out per day (we varied them between breakfast, lunch, dinner, or big coffee/cake stop) but decent enough kitchen to cook relatively relaxed meals for ourselves.
We did a big shop in a naice supermarket en route for easy meals and nice snacks (and nice wine for us), and budgeted for trips to the somewhat expensive onsite market for bits and pieces during the week.
We brought a few dvds (now we'd just download films etc) and board games, and we got the more expensive cottage which was more comfortable, had TVs in bedrooms (so dd could disappear there for a bit at times), and maid service to clean every 2 days (and bread delivery daily too). Dd loves walking in the woods and seeing lots of animals and birds, and just wading into the lake.
It is only a 1 week solution but a surprisingly switched off week for a very busy family.
Or bring a nanny or go somewhere with a good kids club or camp locally that DCs could do for a few hours at least a few days.