Here is a 1983 National Park Service newsletter with a great article on Sesame Place by Sandra Hanna. Ms. Hanna was the director of education programs during the early days of the park and was very influential in shaping Sesame Place at the very beginning.
This article does provide us with some very interesting details. First, it came out in 1983 and it mentions that Sesame Place closes for the late fall and winter months. This is contrasted by the 1980 brochure that explained that they were open year round and only the outside attractions closed in the cold months.
I assume that there was not enough customers that came to the park when it was partially closed. So the park was only year-round for 1 or 2 years.
Also, this confirms that the animatronic Oscar and Cookie Monster were indeed called Automated Muppets. This term had previously appeared in a newspaper article, but we have found flaws in them in the past.
Finally, this article mentions that additional Sesame Places were planned around the country. At this time Texas was still open.
When we were researching the book we had heard from longtime Sesame Place employee Greg Hartley that San Diego was expected to be the third park location, but it never happened. Also, these articles show that Florida was also scouted.