my family had a similar situation after driving from pennsylvania. my wife and i were mid to lower 30's and the kids 10 and 13 at the time, and we are fairly energetic people.
we arrived at the contemporary at around 7:30 am tremendously excited, yet utterly exhausted from driving 18 consecutive hours. we checked our luggage and quickly made our way to the magic kingdom(it was early summer, so the crowds were already noticeable).
after a few hours of fun, we knew it was time to head back and grab a much needed nap. it was just before noon and the time seemed right to head back. long story short, our room was not ready for several more hours- 5pm!!!!!
we explained our situation to the desk and obviously someone dropped the ball. these aren't the standards we're used to with disney. i know the check-in time doesn't guarantee your room until later in the afternoon, but something better than letting us nap in the lobby could have been done.
some of the blame in this situation definitely falls on us here, but just be prepared for your trip. try like heck to have something worked out with your resort before you arrive!
and most of all- have a great time!!!!!!!!