The folks that you work with in pre-planning are not usually the ones who assist you while on site, just an FYI.
For our December trip, I felt that the ladies in the IPO department for the YC went the extra mile for me. I sent down a chocolate gift basket and also a personalized gift for each person in the office. They all work as a team, even though you might have contact with only one "front line" person. If you do a search on concierge tips, you'll see a lot of differing posts. Some have reported that CM's have told them explicitly that accepting cash gifts is a big no no for them. If a guest is insistent, then the money is pooled in an office fund for the entire concierge team.
GoofyGreb, you are already paying for the higher level of service and it's not necessary to tip the staff for everything they do for you. I think decorating a room prior to your arrival probably qualifies as going that extra step though. I had sent down a small Christmas tree from home for our trip and also some presents that I had purchased and wrapped. The IPO staff had me send the package directly to them and they in turn added the park merchandise that they had purchased for me and had it all set up in our room. That's part of the reason why I said "thank you" in a more appropriate way. First, I would check with the staff to see if room decorating is allowed and coordinate sending down the box of decorations. As I mentioned, even though you'll probably only be dealing with one person, they do all work as a team. I think a basket of cookies or somethings that represent your home state would be very nice for the staff.
Tammi