There are many considerations to take in to account when planning your party, what ever kind of party that may be. Does the DJ have independent reviews on Google for example as provenance of his good work ? It is a start ! Is your DJ reliable ? How knowledgeable/ experienced is he in his field. Can you pick all of the songs or give him a huge playlist ? If he/she says yes to that question then he or she is certainly not catering for your crowd. The only person who is capable of making the party work is the DJ and to make the party work he needs all of the tools to work with. By narrowing the field of music to what you the hirer wants, is like asking a mechanic to fully rebuild an engine with a screwdriver and a pencil ! You will achieve the same results .... an ultimate fail !