We have had very god luck at WDW and Flying. Our Daughter has been three times now; 8 months, 10 months and 20 months.
We flew every time and direct flights are FAR FAR better than a flight with stops or plane switches.
Bringing a bottle or nunnie for take-off and landing is good for ears. Timing flights (if you can) so the child is asleep on take-off or landing is even better.
Travel days will be a bit of an emotional issue due to the child coming off their normal routine but patience and things to occupy them are very helpful. Portable DVDs are well worth the investment.
Also as pinted out, finding milk on layovers can be an issue. You are now allowed to bring one (maybe even more) baby bottle(s) with any liquid you want in them, but allow more time to have them get sniffer checked to ensure they are not bomb making liquids.
In the parks, don't plan to do more than one or two things. Anything extra is just bonus. DO NOT miss naps or feeding times if you have a routine. Allow extra time to get the children to bed.
Most of all take plenty of pictures and video, these trips are the absolute best and the pictures and video will provide memories for you and a great perspective for the children as they grow up.
HAVE FUN HAVE FUN HAVE FUN