IMO, the arrival day is a very risky day to plan anything. Never know when travel delays, bad weather, lost luggage, late room availability, etc. will wreck havoc with your plans.
If you don't want to go to a park, personally I would just plan a visit to Downtown Disney. You could make dinner reservations somewhere but make sure it's a place that does not require a deposit and which you will not be disappointed to miss if running late. Also, it would be wise to make sure it's not a place that will require a change of clothes in the event that you get into your room late or luggage is running late. In other words, I wouldn't recommend California Grill, Narcoossee, etc.