A LAV shouldn't be a high priority for DJs. They are not the right mic for live sound reinforcement. A LAV is best suited for video, broadcasting, and recording in the absence of a PA system. LAVS also come in different capsules as well - omni, cardiod, and super-cardiod. The most common cheap LAV capsule is an omni which will be a nightmare to use with the limited capabilities of DJ mixers.
At weddings it's okay for the videographer to use a LAV but, the DJ should be using something else unless he also has a comprehensive head end to process the signal and very good technical skills.
No mics should be open to the subwoofer. If the DJ mixer won't separate this for you then place an XLR low cut filter inline with the microphone. Minimum value should be 60Hz, but 100Hz is better for most males vocals. For females you may even do well as high as 120Hz. There's nothing in the vocals that falls into that range though your mic will cycle all kinds of rumble, noise, and other program content back through the subwoofer and intelligibility will suffer.