The TWR-KW2x board's OpenSDA is programmed with MSD (Mass Storage Device) application, that's why you see it listed as a disk drive.
With that firmware, you can drag/drop .bin and .srec files to the board and that would flash it, but you won't be able to debug.
For the boards to support download/debug features, the firmware for the OpenSDA had to be the Debug App ("DEBUG-APP_Pemicro_v108.SDA").
But PEMicro released a new firmware which supports BOTH functionality in the same firmware. You can also find it latest OpenSDA firmware at https://www.pemicro.com/opensda/
For example: Firmware that supports Debug and MSD functionality for TWR-KW24D512: "MSD-DEBUG-TWR-MKW24D512_Pemicro_v114.SDA".
You can find attached the document with the instructions to modify the OpenSDA firmware on the TWR boards, basically you have to:
1. Unplug the board
2. Insert a Jumper in J30 to put the device in Bootloader mode
3. Plug in the board (Mini-USB)
4. Device will be enumerated as a "Drive Disk" But now with a "Bootloader" label
5. Drag and Drop the .SDA firmware to the drive (MSD-DEBUG-TWR-MKW24D512_Pemicro_v114.SDA)
6. Unplug the board
7. Remove Jumper
8. Plug in the board (Mini-USB)
Now you should see the board being enumerated as "OpenSDA - CDC Serial Port" (allowing you to download/debug) and also listed as a disk drive(allowing you to drag/drop images to the board).
Note1: If the "OpenSDA - CDC Serial Port" driver is not recognized, you can locate the driver within the TWR's Disk Drive (MSD)
Note2: Jumper has to be in place in J29 for debugging
Hope this info is helpful.
You can find additional information on www.freescale.com/TWR-KW2x --> Downloads -> Board Support Package AND BeeKit Wireless Connectivity Toolkit