One of my favorite stories of ring bearers was one of my little brother; Christian was a ring bearer for one of my cousin's weddings. He was terrified because he thought he was getting married to the flower girl. He was extremely hesitant, but eventually persuaded by a giant water gun this size of his torso that my grandma Gertie was holding out in the middle of the aisle. To this day it still one of my favorite family wedding stories. I share this little piece of family history to let you be aware when you have kiddos in your wedding, they have a tendency to think this big party is for them!
Kids have there own schedule but working with them can also be a joy because they are only this little once. For wedding party photos and family photos you want the ring bearer and the flower girl to be ready at the location 20 minutes before we start shooting the full wedding party. In your timeline you want to plan to have them there for long enough that they can be included without it being too much time in between that it is overwhelming for them. If that is too early or interrupts nap time consider doing separate wedding party photo with them after the ceremony.
As learned with my family, bribes are always acceptable!