Fast track wherever you can - passport control etc (no speedy boarding - who wants to be on the plane longer than necessary, especially with kids) Private transfers instead of the coach that stops at every hotel on the island and Sod’s Law you’re the last stop. Throw money at making your life easier wherever you can!
Write off the first day - they’ll be exhausted from such an early flight.
Take water bottles, perhaps a mini squash pod (not sure what they’re called). Plane snacks.
Shop for emergency snacks on the first day. Pain au chocolat/croissants, crisps, fruit, juice, water are good to have in the room. Maybe a small loaf of bread and a packet of ham/sliced cheese, depends how easy food is available where you’re staying of course. My child always wants something before bed.
Turkish towels for beach/pool if none provided where you’re staying. Don’t take up much space in suitcase or beach bag and dry quickly.
Little tube of Dr Beckman travel wash for emergency clothes washing/cleaning swim stuff.
Toys - Reusable sticker books, water pen colouring. Activity packs/books for plane. Uno or Whot (younger version of UNO). Clicky/fidget type toys like a packet of Plus Plus, magnetic tiles/blocks are great, or interlocking building block type things.
I’ve seen some people take little plastic tea sets for the pool as well as sinkers etc. Anything kids can pour from is great. Funnels, buckets etc, tubes etc. We usually just buy a small plastic football at great expense from the on site shop. Rubber rings & a mini pump might be cheaper at home. Don’t forget arm bands/float jackets etc.
Lower your expectations - I used to have a loose itinerary planned in my head and find we could never achieve half of what I’d thought we would. Late nights might mean late mornings, later starts. Kids slow walking - stopping to look at EVERYTHING, takes forever to get anywhere. Embrace and enjoy it, stop to look at the bug on the floor instead of hurrying them up to get ‘somewhere’. Slow down and take it all in. If all you achieve one day is the pool, that’s fine!
The heat can also wipe them out and you mind find mid afternoon naps in the air con a saviour. Make sure you have a good book or something to watch if you and your partner take it in turns staying in the room and you don’t want to sleep. I recommend having a sleep though!