Try and find a spot to sing from where you can be heard but not seen. Finding a focus spot and singing to that rather than watching others will help.

I've sung at funerals a couple of times now, and both times, one or other of these methods has prevented any 'wobbles' until I was finished.

Keep a bottle of water nearby for sipping too... helps with the lump in the throat and dry mouth.

Good luck.

LTS