I dont know. Its a toughy. You could go for more leg space witht he front row in economy, or go at the back of the plane and chance getting more seats. Hmmmm.
I reckon book the middle seat beside the window as you are less likely to have 2 single people assigned to you. Whereas if you book an aisle or a window, its easy to have a couple beside you.
At least its only a short flight. Some colouring books and a sticker book plus some food, and you;ll almost be there!