No, your check-in date must fall between those dates. If you go earlier and will be there over 8/26, you could book it as a split stay, or two separate reservations: 8/22-8/26 and 8/26-8/29. That way, your second reservation would have the free dining.
To get free dining you would need to get two reservations. Aug 22 to Aug 26 and Aug 26 to Aug 29. You would need to purchase a base ticket for everyone in your party on you second reservation.