More/Improved Blog Header and Footer functionality

I would love to be able to add a simple footer to all my blog posts, by setting it in a nice WYSIWYG editor. You can see in this blog post of mine: http://www.theprofessingparent.com/blog/grand-parents the last section of that specific post states: "Are you a parent or grandparent? Does anything above resonate with you? I'd love to hear your thoughts and comments! Please, write a comment below or share this post on social media by clicking the little social media icons below. And if you would like to be informed when I post in the future, subscribe below too. Thank you." I would like to be able to add/edit that text in a single spot to all my blog posts.

Keep the custom header and footer functionality but perhaps on that same page allow managing visible header and footer content in a WYSIWYG editor.