Hi there, Christopher!
With a 2:00 PM arrival time at your Walt Disney World Resort hotel, I would suggest one of three options:
1 - Spending some time recovering from your journey, swimming (depending on the weather at the time of your visit), dining, and exploring your Resort hotel;
2 - Visiting
Downtown Disney for shopping, dining, and live entertainment, and having an early night in order to rest up for the next day at the Parks; or
3 - Checking out
Disney's Hollywood Studios, which is the smallest of the four Parks. This is contingent, of course, upon the number of days you have allocated on each of your
Magic Your Way tickets. Make sure to check the Park hours; it would be a tough turn of events to arrive and find that the Park was slated to close at 7:00 PM!
With younger children and grandparents, I would definitely recommend playing your day by ear. Travel can certainly be tiring, and there's no reason to rush to see absolutely everything in one day, especially if it means having to "encourage" tired travelers.
Take things easy and see how the members of your travel party feel, and make a decision based on moods and energy level.
Happy planning!
See you later, celebrator,
-Deborah B.