How To Fly With Children

In just over 3 weeks I shall be taking my two monsters darlings on, not one, not two, but three planes, in one day, alone.

The three of us, my daughter, my son and I are travelling to the UK to visit my family and I am bricking it.

How in the hell am I going to cope on a plane with two kids, a 21 month old and a 3.5 year old, that can't sit still for more than 5 minutes?

No really, how?  Please tell me.

Have you travelled with kids?

What did you do to cope, what toys did you take to keep them entertained?

And what in the hell do I do about juice and snacks?  Now that you're not allowed to take more than a teaspoon of fluid, and even then only as long as it is encased in a bombproof, concrete box, how can I keep them hydrated, calm and distracted?

Any and all tips much appreciated.