Yes, you will have to use two separate bleed resistors, one for proximity and the other when you want to scan the buttons due to the difference in the parasitic capacitance. I am attaching an example project, where you connect some buttons together and scan them simultaneously. This acts as a proximity sensor as it has a larger sensing area. Once the sensor is active, you can use the remaining buttons for normal button scanning.
I have implemented it on CY3280-21x34 SLM module available here: http://www.cypress.com/?rID=37761. I use the slider area for proximity and the buttons for normal button scanning. Here I am using just one bleed resistor, as my sensing areas are different and I've tuned them accordingly. Also, I am using the shield electrode here to reduce the parasitic capacitance.I turn on an LED when I detect proximity to a finger and another LED when my buttons are active. My buttons are scanned only when I detect proximity.
What you can do with this project is to modify it scan the same sensors. You may require a dummy sensor with which you'll connect rest of the sensors for proximity. You'll just scan that dummy sensor and once the proximity is detected, disconnect all the sensors for individual scanning.
Let me know if you have trouble with implementing this.