We have just got back from a one week holiday, I can genuinely say that I enjoyed this holiday more than any other - it was mostly stress free. Apart from one day, when 2 of my DCs had a quite explosive argument, everyone got along really well.
We got to spend much more time than normal with my teenage son, who normally spends most of his time in his room - I loved that!
It can be hard work when they are little, but you have to embrace the fact that holidays as you knew them will be a distant memory, and not expect them to be relaxing. The key is to keep the DCs happy, and try to prevent hunger, thirst, boredom and extreme tiredness, then everything else will fit into place.
My DH used to be a bit useless on holiday - I did most of everything, and he relaxed. It caused massive resentment, so if I had my time again, I would not let that happen. Also, by the time I'd sourced & packed everything that I needed for myself & 4 DCs, I'd be exhausted before we'd even left for the airport.
Avoid villas with swimming pools like the plague until your DCs are competent swimmers, as you literally can not take your eyes off your DCs; can't even leave the French doors open,which is incredibly stressful.
Beach holidays are different, obviously, because you can pack up and move away from the water.
Forget sunbathing, if that's your thing, for several years.
We had one holiday, when the DCs were much younger, when we seriously considered getting flights back home after 2 days. It felt like a punishment, and cost a fortune, so I get where the other MNers are coming from.
If I had my time again, I'd just go for a long weekend at say, Centre Parcs, with babies or very small children, and then have family days out, rather than going away for a long stretch of time. The most we've done is 10 days, and that felt a few days too long, tbh.