Can I still do the DDP?

I have a reservation for AKL (made through a travel agent). Can I purchase park tickets through someplace like Undercover Tourist and still do the DDP or must I purchase these together through Disney/travel agent?

 

You have to purchase at least a 1 day ticket for everyone as part of the package.

 

The Disney Dining Plan is available as part of a Magic Your Way Package.
A package = room + park passes purchased together from Disney.
The only exception is, Guests staying in DVC properties using DVC points to pay for their rooms can purchase the Disney Dining Plan with no ticket requirement. Guests staying in DVC properties reserved directly through Disney, and for which they are paying directly, must include tickets to make it a package and be eligible to add a Dining Plan.