Hi Flossie, Natalie and I will be flying to Cairns when she is four months old. I'll let you know how it goes, LOL!
Of course you can b/f on the plane. If you are using bottles though, I'm sure you can get help from the cabin staff - they will no doubt have done it before - prob in a container of boiling water?
Wow, it does sound like a big weekend! I'm sure bubs and you will manage just fine. I think every baby is different in terms of how much they sleep etc, but the good thing is that by four months you'll have an idea of how sleepy/active your baby is, so you'll be able to prepare for it. All the best!