Couple notes here. Imagineers do not cut the topiaries. They are involved in the planning and executing of many, many projects throughout Disney, including the cruise ships. And you only reserve the number of seats for your group. You do not pay for 8 people unless you are bringing 8.
In May 07 I surprised 3 friends by treating them to a luncheon with an Imagineer. I glanced up at my souvenir plate when I read your post. It was signed by our imagineer Kevin Thomas after a wonderful, relaxed, informative and most of all really fun experience. The plate was free with the event.
Kevin was an environmental engineer and spoke about how his group selects colors for buildings and displays to go with theming, just to mention one of his activities he has been involved in. He told us how they antique some displays. He was a gracious host and started out by asking each of us to tell our favorite Disney moment. So we got to learn a little about the other guests who comprised our table's group. We were only 4 of the 8.
It is not done daily so if you're looking for a Christmastime experience, you best get calling.
By the way not to spoil everything for you, but you wanted to know if you will get your money's worth - the imagineers are all professionals. You do not get to select who it will be, but I have never read of anyone being disappointed. Your host will answer lots of questions you have.
When you show up for your ressie, be a little early. We received personalized name badges that read "I dined with an imagineer" and our names. Got a lot of comments from people in the park who never saw those unique badges before. This is something I did not know they did until we were presented with them.
You have a waiter devoted just to your group so service will be very good. Oh and your menus will also be personalized with your name. You select food from the Derby's menu so you will have a nice choice of very good food.
Our luncheon started right on time at 11:30 and was almost 2 hours long because we all had so much to ask and learn from Kevin.
If it sounds like it was worth the money - YES! We would do it again!
Hope you book it and hope you and your brother enjoy it.
