IWSG: Switching Gears or Stripping Gears?

It's the Insecure Writer's Support Group Day. If you'd like to join, go HERE. Thanks to Alex Cavanaugh and his co-hosts for putting this event on every month.

So...I'm working on a couple of manuscripts, both paranormal-ish fiction for adults. I have full-blown outlines already written on both. The thing is, I started the Saving Marley manuscript first, sometime last year. Then I had a shiny new idea and switched to the Jump the Grave manuscript.

And now...you probably guessed it...I'm thinking about switching to something new. I want to work on a middle grade book. From the beginning, it's been my intention to write middle grade. I'm even thinking of pursuing traditional publishing with it rather than self-publishing.


Am I switching gears or stripping gears?
Should I finish my first two manuscripts before starting another project? 
Does anyone else have this issue?