I set up PCSX2 with 2 players too! Time crisis split screen works too.
There are a few things to keep in mind:
In the Controller settings, you need to go to the Global settings and tick "Enable Dinput Input Source"
I also had issues with wiimotes disconnecting. Deselect "Enable SDL Input Source". That will stop PCSX2 trying to take over the wiimotes.
I did a separate instance of PCSX2 for the lightguns, to not mess up with the settings for my other games. (you can just copy and paste the whole installation folder)
Then you need to go and edit the ini file:
If you don't have any custom profiles, then you edit the PCSX2.ini file inside the "inis" folder of PCSX2 installation folder
If you are using custom profiles, I believe that would be inside the "inputprofiles" folder of your PCSX2 installation folder
You will need to copy this to the [USB1] section of the ini file (or overwrite if it already exists):
guncon2_RelativeUp = DInput-0/-Axis1
guncon2_RelativeLeft = DInput-0/-Axis0
guncon2_RelativeRight = DInput-0/+Axis0
guncon2_RelativeDown = DInput-0/+Axis1
and this to your [USB2] section:
guncon2_RelativeUp = DInput-1/-Axis1
guncon2_RelativeLeft = DInput-1/-Axis0
guncon2_RelativeRight = DInput-1/+Axis0
guncon2_RelativeDown = DInput-1/+Axis1
(it's likely it won't allow you to save the file directly. Just save it on your desktop , then copy and paste and overwrite)
There's a chance that It's DInput-2 or DInput-3. (You can try and map some of the buttons and see what it will show you.)
Then map all the buttons.
Make sure to map the "calibration shot" button. You will need that for the first step of calibrating the guns.
The first time it asks you to aim, I press the "calibration shot" button and aim at the target at the same time. Not sure if you have aim at the same time, but I think you do.
I have only one issue. Sometimes after calibration, the aim cursor only goes about 85% down, and the more I calibrate the worse it becomes. Not sure why. But it's not really an issue, cause I'm never aiming that low anyway. I think if you are more or less happy with your first calibration, do't try to calibrate again.
Edit: All you have to do is aim a bit higher or lower than you are supposed to, and it will bring the upper or lower borders up or down