Mary,
Awesome post.  Just today I had an employee bring a sales and marketing idea to my attention.  It was in the middle of another conversation about a totally different topic.  I tried to respond politely showing her that I valued her idea, but wish I had used the response you provided:

“I don’t want you to think I’m not interested in your ideas. I do want you to know that I can’t possibly act on all of them, or devote resources to all of them. It’s a priority thing. But the last thing I want you to think is that I’m not interested."

This one goes in my "Communication Tool Kit" for sure!