If you play the level by reviving Agent 47, it can be pretty tough to kill the guards all at once. The best way to kill as many as possible before reloading is to aim yourself to the left when waking. Take the single man sitting in the pew to your left first as you can aim at his head while you are rising. Work your way from left to right while going for as many headshots as possible. This is easier said than done as your Silverballers are stock. Once you have to reload, attempt to take cover outside or up the steps behind you. Make sure the guards with the MP7s are killed first, as they cause the most damage. Be careful because the leader of the Franchise in the wheelchair will also shoot at you.