First, no matter what happens on said journey, you did this to yourself. You decided that taking this gaggle of children on vacation was worth your while, your money, your time, and your headaches. So harness your patience, and breathe.
Second, in any given public place, such as the transfer bus from the airport parking to the terminal, fifty percent of the strangers sitting beside you will find your toddler cute, and fifty percent will wish she doesn't exist, at least not in the same bus at the same time (especially if she's nap-deprived and crying: check). Smile, if you feel like it, at the pro-child contingent. Pretend the other half doesn't exist.
Third, a know-it-all flight attendant, on seeing your toddler cough-choking on apple slices that she is so ravenous for, she forgets to chew, will feel obliged to swoop in, push a handful a tissues in your face, and offer a stern recrimination: "Cover her mouth or you will get the entire plane sick." When you tell the attendant that the child is not sick, just a normal ravenous choking toddler, she will roll her eyes at the horrible offending passenger: you.
Fourth, toddlers who are used to sleeping in cribs don't like to sleep on laps in planes. Not one wink. All day long. "No nap, Mommy." Mommy may feel pangs of jealousy that Daddy is reading a book, while she is wrestling with overtired Toddler. But whenever Toddler is passed to Daddy, she says, "I want Mommy." See point number one, and breathe.
Fifth, children over the age of six are remarkably able to entertain themselves on planes. Anyone who has children approaching that age should think long and hard about having another one, which would revert said parents back into the darkness of having to use airplane lavatory changing tables. And having to keep active toddlers from touching anything in said lavatory while washing hands post diaper-change. Just sayin'.
Sixth, people who paid for an expensive shared airport transfer don't appreciate having a toddler on their bus. Or having to wait while the toddler's parents wrangle with a carseat that is not designed to be attached to a bus seat that has no seatbelts. Or having to wait even longer while those same parents complain to the bus company for promising a carseat and then providing one that is borderline unsafe.
Seventh, and this may be the most important point: being away from home with your gaggle of kids is a hoot. Frustrating and exhausting at times, for sure. But out in the world, showing your kids what you like to do for fun, and without the ringing phone or demanding schedule or homework, you might just remember the joy of being human. And of being a parent. Feeling gratitude for our good fortune to know such joy.