I nursed my daughter for a VERY long time... It was the only thing that made the plane trips ok. Dont expect much protest out of her... expecially if she is still interested in nursing. As soon as her ears start hurting there is going to be only one thing she wants. Nursing will work like a charm.
Caitlin was almost 5 before she had candy, and I gave her dumdums. They are little.
With Caitlin I would hold off as long as I could to nurse, up until take off. Then the same way with landing. If you can keep her just a tad hungry, she will be that more interested. I wish you so much luck, and be sure to let us know how it went!