Lavalier mics are the preferred choice for recording those who are speaking for audio or video presentations. Since the final product will be edited and/or enhanced, it doesn't matter whether you're recording indoors or outdoors.
But for live sound applications, even the best lavalier units can have incredible difficulty eliminating strong wind from becoming audible, and drowning out those who are speaking.
So lavalier mics might not be the most practical option for your situation.
Many DJs love a head-worn microphone because it offers a hands-free option and, because of our job, it really looks cool to many of us.
But if you're one who finds the kind of unit pictured here to be unsightly (which in certain situations, like for clergy at any time, or for a couple getting married, it certainly can be), then you might want to avoid using a head-worn unit altogether.
Models that try to be invisible by flushing to your cheek and protruding straight ahead, are most times the most difficult to hear the one speaking with.
A quality handheld unit is still the absolute best option in terms of getting crystal clear live sound whether you're indoors or outdoors, even in stronger wind.
If you're concerned about the microphone being seen in pictures later on, staging a few shots before or after, without the microphone, might be possible.
This option should be discussed with the photographer, as it will give your clients the kind of keepsake they prefer, while allowing their guests or audience members to completely understand everything being said during their important presentation.