Ooooohh happy memories (not!)
My best advice was to make sure you had help upon arrival to help with any jet lag, especially if you and the little ones need to sleep at different times.
I used to travel back to England (from Alaska) with kids at this age. Having grandparents to help upon arrival was essential.
Other tips:
Toddler slept best in light weight car seat - head support and 5 point harness always helped.
Take more nappies and spare leggings/tops (including for yourself) than you expect to need.
If you run out of nappies, ask another mum on the flight.
Small toys, brought out one at a time - play doh, fiddle toys, books, crayons, popular (but not irreplaceable) soft toy.
Never underestimate you inventiveness... I once ended up creating puppets out of sick bags, and the laminated 'in an emergency' card can buy you at least 10 minutes entertainment.
Good luck!