Get referrals from people with kids
This is a sort of short cut that helps you narrow down your options. A one on one description will also capture more information than an online review. Talk to people with children who are close in age to your children. They will have some good advice that is based on their own experience.
Online reviews will also give you some information you may use. This is especially if they mention outdoor sitting areas and child specific menus. Be keen on noting the opening and closing times so you are not inconvenienced. Take more interest in the customer reviews as opposed to the restaurants' own advertising.
Visit some restaurants by yourself
Have a meal at a few restaurants by yourself. You can start with the top choices that were recommended to you. Check out everything that is on offer on the menu. Also observe their seating arrangements and what their ambiance is like. This will let you know what to expect if you come here with a child. Go on a weekend in the afternoon so you can see if there are any children present.
Check the pricing to be sure it fits into your budget. Also, be sure that children are allowed because some high end restaurants forbid them. The two main things to consider will be the menu and the ambiance. When you visit these restaurants, get the following information.