You mentioned a few things, here is what comes to my mind:
-LEDs, smart thermostats, motion activated lights, proper insulation for windows and doors
-plant native trees and bee-friendly things, dont mow grass
-collect rainwater to water the plants
-Install an insect hotel
-community gardening, grow food
-install a pond
-in case people come by car: encourage walking/biking/public transport to church, offer good bike parking
-solar panels
-avoid plastic in general
-buy stuff used and dont buy everything new
-encourage sharing stuff in your community like tools, cars and so on
-invite experts to presentations, talks and discussions and invite everyone
I never went to a church, so I dont know whats going on there but if you have any type of event:
-offer vegetarian or better vegan food only, seasonal and local (this is probably the most impactful)
-no single use cups, plates, bowls, cutlery or but get resuable stuff
-no bottled water, no plastic bags