Dee,
Very cool to hear from you! Thanks for writing. It was nice to meet you as well at MagicMeets last weekend at Camp Hill, Pennsylvania. It was my first time attending, but I'd definitely do it again. Amazing to hang out with so many people who really "get" Disney.
Regarding the stool, unfortunately it seems that you can't bring in a portable stool. Disney specifically lists "folding chairs" as a prohibited item to bring into the parks, and I think a portable stool would fall under that description.
In case you (or others) want more details, you can find a more complete list of prohibited items click
HERE to find Disney's Theme Park FAQs. The last Q&A on the list is "Are there any personal items I should not bring with me into the Theme Parks?"
Hopefully that info helps, and I hope to see you again next year at MagicMeets! ºoº