Rest assure, your kids will behave. They'll behave like kids do and that's by being unpredictable. Being that thankfully I have a family of my own, I so get you and your kids! "Play and Praise" is my motto and I love to set that tone in my studio as well.
Although it's best for parents to prepare their kids in advance as much as possible, it's also important to let go. Let your children just be children.
During your sessions, I get to know, interact and play with your young ones so our time is enjoyable and memorable minus all the pressure to "behave". Some kids need more time to get comfortable, some kids need more breaks between sets, still others like to explore new surroundings. By working with them in their way, I focus to capture their calm and happy smiles and/or their fun and mischievous personality accordingly. Healthy children work in a variety of ways and that's why I don't time or limit session slots.
Get ready to see their personality captured for eternity!