Hi Lisa,
Your trip will be here before you know it! I love using
Disney's Online Check-in Service - its so easy and makes the process super simple and super fast once you arrive. The person whose name is on the reservation will have to present his or her photo ID. They will give you a folder with your Key to the World Cards and resort information.
When I did my online check-in for my last trip, I did list that we were arriving earlier than 3 p.m. We actually ended up getting there even earlier than I expected. Our room wasn't ready so we grabbed our swimsuits and headed to the pool. They sent me a text (they will call you on your cell if you prefer) to let us know when our room was ready and gave us our room number - that way we didn't have to make another trip to the lobby and could go straight to our room once it was ready.
The trip before that, we were later than our estimated time of arrival (yes - I'll admit it - I was too excited and took the wrong exit getting off the turnpike). That wasn't a problem either - our room was ready and we headed up to get a good night's rest before heading out early the next morning.
Check in for the resorts is 3:00 p.m. Keep in mind that even if you list you are arriving early, it doesn't mean that they will have your room ready. If you get lucky, it might be ready. If not, you are welcome to start enjoying the resort amenities until it is ready.
Give them the best guestimate you can knowing that they will help you work it out once you arrive - whether your earlier or later than expected. Wishing you many magical memories :-) Allison