Will straightening my nasal tip in Rhinoplasty be enough to straighten my septum too?

It is difficult to answer your question without seeing your pictures – you should consider posting images showing different views of your nose.  The tip and the septum are separate structures and most often they each need to be dealt with independently 

Dear irsiThe nasal tip has multiple support mechanisms. The nasal septum is one of the major support mechanisms and is sometimes reinforced by further strengthening with addition of grafts. You septum divides your nose into two tubes and plays a role in breathing if its deviated and blocks the air or due its lack of good attachment to the upper lateral cartilage, contributing to valve collapse. Tip and septal surgery in general can be performed independent of each other except in specific circumstances.

A rhinoplasty and a septoplasty are 2 completely separate operations. A septoplasty is performed for medical necessity to improve breathing out of the nose. A septoplasty will not change the shape of the nose. To straighten a crooked nose requires a rhinoplasty. The rhinoplasty can  address straightening the crooked tip with a tip rhinoplasty, cartilage grafting techniques along the mid vault area when there is a collapse, and osteotomies performed in the nasal bones when they are twisted as well. For many examples  and more information, please see the link below

The septum is the support to the tip of the nose. In order to address the tip, it is much better to address the septum first - this provides a stable base for the rest of the nose. I would recommend an in person examination to see if your septum is the underlying issue, or if other things need to be discussed to address your concerns. Best of luck