You will probably be able to experience the fringes of the F&W Festival, Jennifer. Since you plan to go to Epcot anyway and you will be walking around the World Showcase, the food booths will be all around you. The first time we went to the F&W Festival (11 years ago!) all we did was eat and drink a few things while we were walking around. We enjoyed it all very much. There will be booths set up specifically for kids so Olivia will enjoy herself at those too.
Sorry, I can't help with the Behind the Scenes Tour. Is that the one you have to sign up for outside of the Soarin' entrance?
This one is posted on the disney site under family but it did not give details about where to sign up or how much. I know their is one that is behind the seeds. I think this one is a little different but could be wrong. It starts on the 26th. We will be their the 26th to the 28th for park days. Do you think we should avoid Epcot on the 27th and 28th as those are Sat. and Sun.? I some how did not realize it would start while we were their