You need a separate DVD player so you can connect the output of the DVD player into the input of the TVG and connect the output of the TVGuardian into the input of the sound system.
This issue is TVGuardian needs to be connected between the source and the TV and/or surround sound receiver and there's no way for TVGuardian to intercept and mute the audio with a built-in DVD Player. You can connect an external Blu-Ray or HD Upconversion DVD Player to the BOSE (or other brand DVD Player / Home Theater Combination unit), and it should work fine. An HD upconversion DVD player with HDMI and the yellow composite cable connection is required.
Looking at the BOSE system, you would connect TVG to the BOSE using a optical digital audio input (Toslink) cable.