First off plan your flight for around 1pm, if possible of course. Then, beginning two days before your flight make sure your 2 year old wakes up at least 10 times throughout the night coughing for 2 nights in a row and make sure she misses her nap both days as well. This might cause a little crankiness, but it's worth it. Don't have your 1 year old skip her naps though... That would result in chaos. However, make sure the 2 little ones sleep close enough that the crying 2 year old wakes up the 1 year old a few times through the night. (Oh and make sure your brother comes home and makes enough noise to wake up the 1 year old for an hour or so... This is key.)
On the day of your flight go about your day as normal except make sure the 1 year old does not get her morning nap. (That would completely ruin the plan) Get to the airport plenty early so you have enough time to eat lunch and take everyone potty and change diapers (if you can get them to poop now that is preferable) and get back to hear them call your name. (Oh ya, make sure you are flying standby... It adds much needed stress) And don't forget after all that is done and you are sitting down that the 2 year old will again tell you she has to poop. Which means packing back up the stroller, bags, and babies and heading back into the bathroom. Then walk back out just in time to hear your name called. Hallelujah!!!
You get your seat assignment which has your 2 year old sitting by some stranger and when pointed out to the gate agent he tells you to ask to switch once you get on the plane... (Lovely) The lady agreed after pointing out that she does not like the window seat but would still trade. Thank you?
Next get settled in, tell the 2 year old at least 16 times that she has to sit down and keep her buckle on... Kind of like your carseat except that you are capable of escaping. Fiddle with both kids while trying desperately to keep them quiet and from instantly annoying every person on the plane. Cave in and give the 1 year old her bottle while taxiing so it's gone before the flight ever takes off. Listen to the 1 year old cry as she poops.... Again!!! Debate whether the poop stinks worse or the guy in front of you that showered in his cologne this morning. Set the 2 year old up with her pillow and blanket and watch her fade into oblivion as the 1 year old squirms and whines because she's tired but is being kept awake by a certain stench. Wait in a line to use the one lavatory which does NOT have a changing table. Squeeze into the tiny potty sit on the toilet and attempt to change the poopy diaper without getting any on yourself. SUCCESS! Go back to your seat snuggle up the 1 year old and enjoy the rest of the flight. Even get a coke if you have a free hand.
Follow these steps to a tee and you will have a successful flight with a 1 and 2! year old. Good Luck!