Sorry if my question seems daft, but why aren't you able to check in until the afternoon ?
Do you have something you need to do in the morning, or are you just sticking to the "rules" that say check in time is at 3pm ?
You can always do early check in. All you need to do is do Online Check In for YC (used to be 10 days prior to arrival, but it seems that it's going to be extended to 60 days due to the new system) and select the earliest time you want to check in.
When we have our first nights offiste, we always select to check in at 8am. And each time our room was ready
The 3PM line really tells you that you are not guaranteed to get your room before 3PM, but they will do all they can to get your room ready before that if you so request (during online check in)
worst case scenario, your room is not ready, and you have to leave your bags with the Concierge or Baggage Service (and can also arrange to have them deliver to your room once it's ready)
you'll get your room keys and can be sent a text message with your room number once it's ready, but you would already have your park tickets and your dining plan credits (if you have any)
I might be totally off topic here, since you might have good reason not to want to go to YC before 3PM, but if it's only a matter of what's written on your booking confirmation, then note that you can check in early. As early as you wish actually (unless YC has a different policy than the rest of WDW hotels, or if the new system has taken that perk off ... it's worth checking it you still can)