I used to shoot for my ministry too, so chip in abit.
if a reshoot is possible maybe can try to 'position' your people into the 'good spots' before the service begins and of course brief them to be more 'expressive' during that particular worship session. Maybe can ask the youth groups and church leaders(Young and Elderly, generally the more 'ON' folks) to come for the same service to make the picture happen? I believe the leaders are more than willing to lend you a hand to get these people together.
This may seem to be 'posing' for the pictures, but pictures with happy people will also remind people that P&W should be a happy thing. So instead of just a picture to show what's going on, let it also become a form of encouragement and reminder to the community.
Even if everything don't workout, there are always many other ways to overcome them. Do not lose heart.