I love our family holidays (3dcs, aged 3, 5 and 8) and am on total countdown until we go away at the end of the month...
But you do need to 'manage' your expectations. Not so much revise downwards, as just know what reality will look like.
So, for me, that means I prefer to be self-catering, rather than in a hotel, not because my dcs won't behave (they will) but because we enjoy slow mornings and breakfast in pjs; self-catering means we have the option to take picnic lunches to keep costs down, and (best of all) means I can give the kids a light, quick, easy supper (grilled fish, omelette, pasta...) that I know they will enjoy, after a quick bath (and back in their pjs!) after a long, tiring day on the beath or sight-seeing.
Yes, it means I have to do all the 'heavy lifting' on the cooking front, but it leads to a generally happier, easier (and more relaxed) life all round.
In the same way, we will fill our days with a mixture of beach visits, local town (mooching), some proper trips out to the local area...but the dcs know we're all on holiday (not just them) and dh and I get a say in what we do, too.
To be fair, we'll never be 'left alone' on the beach but dh and I will take it in turns to build sandcastles, collect shells, go swimming in the sea, and the other one will lie back and enjoy 30 mins quiet time....
But back to expectations for one moment: I started enjoying family holidays so much more once I decided that what I wanted to get out of the holiday was lots of time with my dcs, rather than escaping from them.....(although that could also be good....
)....but by resetting my aims, I suddenly found I could have a lot more fun.
If it doesn't work for you, though, OP, then save your money and just don't do it :)