In December 2012 I flew to Melbourne with my husband, our then 2.5-year-old and two-month-old, and it was one of the nicer trips I've taken with the kids. As the breastfeeding mother, I was able to relax, feed the baby and watch movies while my husband did laps of the plane with our toddler (good man!). So the flights could actually be quite enjoyable (for you, ahem). I had access to a bassinet but I actually found it more comfortable to use the sling or just hold the baby - ask for lots of pillows.
In June this year we flew to the States for a wedding and it was quite a different story as we were schlepping all over the country with United Airways and I had a wriggly 8-month-old to handle. Every single time we went to check in the staff would casually announce that we were all seated separately despite our best efforts to check in online and arrange to be seated together. However, each time we made a minor fuss and were reseated, often in the economy plus section. So it can actually work out in your favour.
Have a great trip.