I make pretty big meals for my kids and they seem to not get full. They want 2nds and 3rds most of the time

Beans, seriously lots of Beans. People at my job were just talking about it today. And there a chapter in Steinbeck's book Tortilla Flat were all the kids eat are Beans and they are super healthy....

foods that are too high in carbs tend to make us eat too much (pizza, pasta, fried rice). pasta is a good example, you can eat a giant plate and still crave more. a balanced meal should visually look like 50% vegetables, 25% carbs, 25% meat or other protein.

protein. lean meats. potatoes. beans, lentils, legumes, rice. you can buy all of these things in bulk.

Well, things like,
Rice
Potatoes
Pasta
And breads "pad" out a meal...make it go further.
Also stodgy doughy things like dumplings, gnocci and pastry are very filling.

Nachos w ground beef.
Hotdogs
Burgers
Chicken tenders

Kids are always hungry. As long as their meals are nutritionally complete and healthy, don't worry too much.

Do they have milk or something while there eating, it helps to fill up that empty stop, I drink alot when I eat and it gets me full

Rice, milk, bread, pizza and vegetables.

Rice-A-Roni.

How old are they?