New idea, old brain

Well. sticking to my guns about better characters and stories for Tweens, I have an idea in my head that needs to be developed.  this will mean some work on an outline or blueprint. .. characters, setting, problem to be resolved, how it's resolved.  Will this story be one that keeps the reader engaged?   How do I know I'm on the right track?  I'm still happy with my Picture Books. I really think that 1 of them in particular has real merit, but wow; am I ever down on my other stuff.  so many changes to make that I wonder if they should just be scrapped.   I think the gloomy foggy weather has entered my brain.   Maybe some coffee and an old fashioned pencil and notebook will get me started working.  Sitting at the computer hasn't worked today, but I do share the Scarlet philosophy..."Tomorrow is another day."