Let's all (do something)

This is how you suggest what to do to a group of people:

Let's all think it over tonight, and we can make a decision tomorrow morning.

You use "Let's ~" when you're pretty sure that the people you're talking to will take your suggestion. They might do that because you're their leader or boss, or they might follow your suggestion because it's easy to follow or a clearly good idea.

take a step back and (do something)

To "take a step back" means to think about a topic in a more complete, less emotional way:

I was extremely upset when I got laid off, but after a few weeks I was able to take a step back and realize that I still had what was important - my health and my family.

If you take a step back and think about it, college doesn't really last that long. It's just four years out of your life.

Do you ever take a step back and wonder why so many people wear glasses in modern times? Our ancestors wouldn't have had glasses, so how were people able to see back then?

it's about (something)

This is a way of telling people what the goal, purpose, or key to something is.

To use this, the topic needs to be understood by everyone. As an example, if you're talking with someone about learning English, you can say:

It's about building up your vocabulary to the point where you feel confident talking to people about any given topic.

If you're talking about cooking, you can say:

It's about getting the freshest ingredients.

what's best for the children

Raising children is very important for a lot of people. So teachers, politicians, parents, and other people often talk about "what's best for the children". They think about "what's best for the children" when making decisions.