1) Unless staying Concierge Floor at a Deluxe resort, nothing gets sent to the room before check-in.
2) Ahead of check-in time, their room number is not assured.
3) And, sometimes, even not when staying Club Floor.
4) But, you can arrange for something AFTER they have checked-in.
5) The Front Desk Runner will deliver either
. . . on their normal time and route
. . . when the have spare time
NOTE: I almost all cases, only the Front Desk Runner can enter rooms to deliver items, except for occasions on Club Floor when the Concierge does it. Even if you order from the WDW florist, they deliver to the Front Desk and the Runner delivers. The moral of the story is be VERY kind to the Front Desk Runner.