I travel frequently alone with my two children. It does not have to be a problem, in fact it can be quite enjoyable. I just have to plan what i bring for entertainment. Crayons, paper, colouring in book, books (not puzzles as pieces get lost) a few toy cars, important thing is that it is all new and not been played with before.
Each child have their own little travel rucksack, where they have packed lunches (not sweets, it will make they haywire and queesy), fruit, drinks, toys, books, crayons, etc. Looking at airplanes, pointing out what we see in the airport, talking about where we are going, what we are going to do there, we make it into an adventure.
Can you spot the bag on the conveor belt? Who can see it first? Can you help mummy find the passport control? Where do we check our bags in again? Who can spot the cafe for a spot of lunch before boarding the next plane. Do you think there is a playground here? What can we buy as a gift for granny/aunty/cousin etc....
My friend got her travel nanny on Gumtree, she was 37, experienced, and a real pleasure to be with on holiday in france, according to my friend. If you can afford it, and dont think you can do it on your own, try place an ad there.