I generally don't use the IPO for dining reservations. They don't have a system that constantly looks for reservations like Touring Plans. AFAIK, they look once or maybe twice a day. I think I have a much better shot getting difficult reservations by quickly looking myself multiple times or using Touring Plans.
That said, they were helpful in getting me a specific reservation at Flying Fish. I was keeping an eye on my
MDE, though, and knew that if something didn't pop in I knew I would need to look.
For something like wanting to order a cake I'd look at the cake thread on the restaurant board.
http://www.disboards.com/threads/official-disney-cake-chatter-part-iv.3261922/
I've used it before, lots of great info in post #1.
For flowers/gifts I'd check with Disney Floral.
http://www.disneyfloralandgifts.com/
I've found that if I want something pretty specific on a particular day it's easier and quicker to just make the selections myself. It gives me a first hand look at the range of options and at what cost. A lot of email back and forth takes time.
Your other option would be to call the IPO and discuss your requests. Often I've found that they are more helpful over the phone.
From your siggie, it looks like you're staying at the Grand, is that right? I've not stayed there. I do know there is a wonderful Grand Floridian resort thread on the boards. The folks there may be helpful, too with ideas for your requests.