Those little boys that run around the wedding that are usually part of the wedding party are not just there to play but to actually run errands in a really cute way.
The ring bearers and the page boys traditionally are children aged four to eight and they both have different things to do.
The page boys are usually there to help carry the bride's train if its extra long while the ring bearer walks down the aisle with fake rings tied to a pillow because you can trust a bunch of kids with the most important jewellry that is needed at the wedding.
If you've no clue on how or who to choose. Don't sweat it, you can choose your god children or your cousins's kids. It's a good way to involve the little ones in the wedding party and the whole celebration.