I agree you wont get an upgrade with kids, you are lucky to get 1 upgrade but travelling as a party, never.They tend to pick a single traveller so as not to split families up and believe me there isnt a trick in the book that they havent seen before.
If I was you I would go for 1 aisle seat for yourself and seat the younger two opposite you in another aisle seat and the next to it., then if they play up or start to argue you can put them apart, by changing seats with one and thus seperating them.Its quite a long flight so make sure they have plenty to occupy their minds.
Window seats are great for about 10 mins then all you see is clouds and if you want to get up you often have to wake sleeping passengers and it becomes a pain.
Good luck.