We went for our Anniversary last summer, stayed at the Poly, ordered from WDW Florist. I understand from all the posts on the Dis, they do not "pre assign" rooms, so you check in and get your room assignment... knowing this I chose to have my arrangement delivered "after" check in... I know check in to be after "3pm" and we got to Disney before noon...
So while I got us out to the parks at 2, we returned, and there was our "surprise" floral arrangement, and bag with treats for DD (I also ordered from WDWflorist!)
I know Peggy from Peggysweets, aka feralpig has also posted she delivers to the front desk from 9am till noon... so if you arrive they note it on your ressie, and will give it to you upon check in... I prefer to have the element of "surprise"...
HTH