I find that my kids tend to eat more if they control what they order (within reason of course). I have them read through the menu, decide what they're indeed craving, and take part in ordering.
When they’re young, I think letting kids play a little bit or walk around before the food arrives helps them sit more calmly in the high chair when it’s time to eat. Of course, feeling comfortable letting them play is a challenge! So even though we don’t typically eat early meals, sometimes going to a restaurant earlier in the evening or lunch time avoids the rush. I think just having a little extra space with fewer people can make the entire experience calmer and totally worth the off hours!