Small families typically are the easiest to photograph with older children. They can be positioned and listen well to achieve a flawless photo. I find with younger kids it's much easier to just allow them to do what they do put them in the area you want them and then allow them to be kids talk to everyone in the family and move around a little the photos will be more effortless and pretty.
I love for children to being props will help such as a small toy that would blend with the photo. I also like to hold a variety of stuffed animals . I being a few different ones because sometimes kids do not always respond to the one you pick. I try to pick a character that allot of kids know. Olaf from frozen is popular so he has been the best animal right now. Having toys that squeak or rattle are good to have for children under 5. I like to bring small stools or chairs also for the kids to sit on.