As someone who has seen both sides of travelling with young'uns, where other people's kids can drive you mad, or when you're trying to keep your own entertained, you may find sitting towards the rear is helpful.
The reason I say this is that you only have the people in front to worry about upsetting and causing you problems. I'm the type to stress out about others so this can be a weight off your mind.
You may also (on a free seating flight) wish to sit near another family. We did this and were able to swap toys/pens/books and the kids kept themselves amused for a bit playing hide and seek between the seats.
Flying for the first time can be a nerve wracking experience, particularly the first takeoff, with the noise and acceleration. Nobody knows their kids better than the parents but we found making out like the takeoff was the most fun thing IN THE WORLD EVER with HUGE smiles and laughter turned a worried face into a smiling one.
We also had an issue when the takeoff involved a turn over the sea. Didn't like THAT very much and the word crash was used a few times so reassurance is vital even when you think you have it nailed.
Pick your moment wisely but a walk along the aisle can be a great idea, particularly if you can chat to a delightful easyJet cabin crew member in the rear galley.
I've heard of others who have kept children awake with the intention of them sleeping on the aircraft. I guess this might work well, but if it doesn't you're going to have a very cranky kid on your hands, so I'd go for the entertainment option everytime. As said before burning off excess energy in the departure lounge is a great idea.