OP, I completely understand how completely unfair the situation is with your ex and also how that is impacting on your holiday now. However let me share this with you..
DH came from a family with little money and 3 hard working parents. Their holidays were always camping in Cornwall come rain or shine. For 1 week a year. And goodness me he has the best memories. He talks so fondly of it and everytime we go away he has tales of his childhood holidays and all their adventures.
I on the other hand when to Florida every year, to sea world, Disney kind, or a villa in the algarve etc. And I was voted silly. No other kids to play with, mum and dad are wonderful, but they don’t know how to be silly with kids. Honestly I dreaded holidays and it breaks my heart when I think of how hard dad worked to pay for them.
But what I am saying is, holidays are about who you are with and not where you are. Find some stuff to do tomorrow with the boys, if they haven’t made campsite friends. Are you near a Beach? You could buy a kite for about a quid and fly that? And laugh about how rubbish it is. Crab fishing? Plan food for tomorrow, a disposable bbq is only a few quid in Aldi and then you can bbq sausages?
Bless you, I totally understand how you feel, but I think it’s less about camping and more about the unfairness of your ex.