Plated dinner and children.

I think ChristineKyle's idea would work well-- no one knows the child's appetite better than their mom. I think if you put up signs that the snacks are for the little one's, people will get the drift and enjoy the adult appetizers you're providing for them instead of stealing from the kid's table.

Your caterer should tell you what ages you pay for and dont. On the meal selection, just put "___kid's meal (chicken tenders)" so the parents know what it is.

Age cut offs are normally set by your caterer.

(ours is under 12 is a reduced rate on an adult plate, under 8 is a kid's meal)

But if yours doesn't do different tiers, agreeing with previous posters.

Our cater asked us to pick one option for kids (over 3 and under 10). I think we're going with pizza. But kids under 3 typically can pick off parents plates or parents bring snacks for kids. A kids table might be tough for younger kids that need their parents direction for eating and staying on task. I could see a kids table for older kids (maybe above 8 or 10), but not younger kids. They just go bonkers if they don't have parents around to keep them on task.

Ask your caterer. Ours offers a children's meal for ages 2-12. If they are 2 years old and up they are included in the head count and we will be paying for them at the adult rate unless they want a kids meal. Your caterer will probably have suggestions about how to offer the kid's meal option to your guests too.

"Grazing off mom's plate" is not an option for anyone with kids lol. You should include a kid's meal option on the RSVP card. Parents will either check that option, or they will bring baby food for their child to eat.

ETA: what is the age range of kids you are planning to invite? Its probably best to seat kids with their parents to make sure a) they are not running around and are respectful during appropriate times, like toasts and special dances and b) actually eat