Diana,
Thank you so much for coming to us with your important question. In my experience, Walt Disney World goes above and beyond to accommodate diet requests. To provide you the very best answer, I'm going to direct you to the
Special Diets team. I think it would greatly benefit you to have a game plan of the "official" locations able to accommodate your family.
I've received prompt, detailed responses when asking specific questions to the team at Special.Diets@DisneyWorld.com or by calling them directly at (407) 824-5967.
My guess is Be Our Guest will be able to accommodate your son's pureed lunch, but best to check with the team.
Any other questions, Diana, I'm happy to help.
Wishing you a magical vacation!
Sherri