I think this depends on a lot of circumstances
Age of children, what they want to do, what will make it a good holiday for them, how active they are.
If you are constantly watching a baby,toddler or small child for safety/water issues it's not very relaxing. If you get on the beach and they want to go back after an hour cos they are bored, it's not very relaxing. They don't all play nicely on the beach.
A holiday with my H, yes we have to have kids clubs, because it's our holiday as well, and we need to relax and enjoy time by ourselves. However DS loves it, and it's only a couple of hours here and there, and he interacts with other children. And he can only do an hour or so on the beach, or an hour at the pool before he gets bored. We still have hours and hours of play time with him.
If he didn't like it, there's no way on earth, I would leave him there.
If I holiday with my family, then no kids clubs, because we all muck in with looking after them, and the kids together amuse themselves. And my mum is super-Grandma!It's a lot different with more people there.