Seating Arrangements for Kids

I'm not really sure what to do with the kids at my wedding. All of them are so different and some are young, 3 and 4.

Do you seat all of the kids together (ages 3-13) or should you put the families with kids together.

Do parents expect to get rid of them at other tables so they can enjoy the evening?

I'm the first of my friends to get married so I need advice.