Take something with you that they haven't played with for ages or buy something new. We took a few things that kept dd occupied for a good while, as it was new! We took play dough for dd, not sure if you can now, with all the new rules tho.
Take changes of clothes for everyone in hand luggage. Dd (20mths) at the time, spilt milk all over dh, who didn't pack spares (he didn't think he'd need them) luckily, I had some for him in my carry on!
We stayed behind until everyone was off, as it was easier than fighting with everyone to get off.
If your 2yr is in nappies, consider pull ups for the flight. I hate pull ups, but they were a god send in such a small place!
And please don't rely on them sleeping. It is all very exciting & different. Dd didn't sleep much at all. I don't say that to be difficult, but lots of people seem to think that a night flight will make them sleepy. Dd was awake most of the day & sleeps very well at night, just not this time!
Snacks, snacks, snacks! Most airlines are great with children, but having flown several, they never seemed to have what dd wanted. She couldn't eat at the set meals times (body clock all over the place) so we kept anything that was sealed & offered her that when she wanted something!
Some may recommend giving your children a sedative of sorts (I think piriton is popular) but it can also have the opposite affect! Keep sugary foods to a minimum.
Very comfy clothes for all! We travelled in joggers & Ts. Don't underestimate comfort!