Hey, Lou; Keep it simple. Get the pastor's approval and assistance.
BG?...easy: wall of the church...interior-exterior, makes no diff. Some churches have draperies that do well for BG, keeping in mind the reverence appropriate in the chapel.
Seated or standing, move the subjects away from the BG, & use a shallow DOF (large f/stop, like 2.8) to isolate the subjects from the BG. Or...go to a quilting shop; they have marvelous 108 in. wide Batik material in mottled shades. buy a couple of yards, tape it up, again, subjects away from BG so it isn't in focus.
Emphasize the mother.
Other members of the group(s) facing towards the mother. Not looking directly at her, but turned slightly to wherever in the composition she may be. Kids...have a funny, squeaky toy for those that just don't wanna cooperate. (Leave the whip and whistle at home!

)
Single Flash...Off-camera, ittl cord if you have it. On a bracket...raised as high as you can, and off to the side, within the limits of the bracket. Off-camera...arm's length, either side, one-hand the camera. Steady on, there!
If you are lucky enough to have one...Voice-activated, carbon-based light stand...(your assistant

) camera left or right, flash about head high. Closer makes for softer light. Diffuse' em, if you got 'em.
Like in debate: Be Brief, Be Brilliant, Begone!
