We have yet to use the bathroom on the plane. We are flying from STL to MCO. Not very long. Also, we *always* make the kids go before getting on the plane.
My kids like the little bit of one on one time with their parent. I spent my time talking about the trip and what we are going to be doing. (what ride are you most excited about? This time I want to find the Incredibles in MGM. That kind of stuff... ) Dh is usually teaching 'his' child a different card game or trick.
* You may or may not need birth certificates for the kids. Bring copies anyway. You need a drivers license for both yourself and dh.
* Wear loose comfortable clothes - skip the belts so no one has to take them off for the security check. Slip on and off shoes are good too (in STL they request we place our shoes in a bin for the xray machine).
* Curbside checkin is almost always faster than going inside.
* Have a luggage tag on and in each bag.
If you do not sit with your kids, just know that they may be frightened by the loud noise of the engine, and the landing, since they haven't experienced this before.
Just a request from a frequent flyer... would you consider sitting in front of the kids? Then if they kick any seats, they won't be disturbing anyone else. (My ds had the tendancy to swing his legs without even realizing it, so we always put dd or dh in front of him. **Disclaimer** I am not making an observation about your own children - just making a recommendation based on my own son.)
Let me know if you have any other questions!
