How do you keep a toddler busy during a flight so she won't run back and forth to and from the lavatory?

I suggest according to the interest of your kids, take the toys, books or other things they get engaged with the most. It is a good idea to tell them beforehand what all to expect in a flight. This way they would not complain and sulk about getting bored during the flight. Yes, you can also take activity book with different activities in it. If you are not averse to giving gadgets to your kids, you can download some cartoon movie for them and have them see it. This will take care of most of the hours in the flight. Get them some snacks, and they will forget any discomfort if there be. http://www.essentials.co.za/lifestyle/keep-children-busy-while-travelling