I don't have children but I do have a nephew and niece who I love very much. When my nephew was first starting to walk, he would go from a stationary start to running almost immediately. And he would run with his arms thrown back, unafraid of falling. That's what the best improvisers look like on stage - tilting towards the horizon, arms trailing behind them, unafraid - secure in the knowledge that if they fall their team mates will catch them. You can't keep your eyes off someone who performs like that.
The idea embodied by yes, and is one where we accept and build on the other person's idea.
YES - I've heard your idea and I love it AND here's another idea that your thought inspired in me.
When we improvise in this way, it's like we've networked our heads together - to think bigger thoughts than either of us could have thought on our own. That's what accepting & building does - it provides a way to connect us to each other.
When you enter a scene, your character knows more than you do. As an improviser, you are stepping into a blank space - you don't know who you are, where you are or what you're doing. You're in a liminal space between reality and fiction. Your character, in contrast, knows everything about the scene - they know who they are, they know who they are with, they know where they are and why they have come there. We want to close this knowledge gap as quickly as possible. And do often we put questions into the mouths of our characters - questions they wouldn't ask because they obviously already know the answers.
Who are you? Where are we? What was it you just said I wanted?
It's a crude strategy to get the improviser on the same page as the character. And it's clunky as all hell. Far better to just assume knowledge of the situation.
Make assumptions about your scene and, as there is no objective reality, by the power of improv they will be transmuted from mere speculation into concrete fact within the world you're creating. You get to the same place of agreement but you don't have to ask question or put the burden of creation on your scene partner. Lovely.
Here's a quick trick that seems to work. When you want a scene to be more theatrical - just tell yourself that this is a scripted piece of theatre. Believe that you have rehearsed this scene for many months - that every line has been crafted by a playwright, that every move and line reading has been discussed with a director. Flip the switch from I'm making this up as I go along to I've been polishing this performance for weeks. It's such a simple trick of the mind but it produces such different results, it's almost magical. Your dialogue becomes more beautiful, thoughtful and poetic. The decisions you make about plot and character are simpler and more fulfilling.
Free yourself from the expectation of what improv needs to sound or look like. Because it can be anything you imagine.