Flower girls and Paige boys are a lovely inclusion in your ceremony. The truth is that most of the time, they are quite young and struggle to stand up at the front of the ceremony for the whole time.
I always say, if you think they are too young to stand up at the front, then get them to sit down for the ceremony.
However, make a point of acknowledging them as they walk towards the groom. I ask the groom to give them a high 5, or a hug and then have them sit down. That way the photographer will get photos with them in it. Otherwise, this element will be missed and you may only get a few photos at the very end.