Booze and hunting don't mix
As a hunter, I'l tell you that booze and guns are a VERY dangerous combo. If there is even a chance that your EX might be drinking... it is definately not safe for him, anyone with him...or anyone even remotely near him... to be out in the woods.
Gun safety is pretty much like driving....it's all about alertness and awareness.
I can't tell you whether it's a good idea for your EX to be involved in your son's life.... but if you decide it is....how about a nice safe, supervised environment.... maybe with a responsible 3rd party present.
Do you have any mutual contacts that you would actualy trust to make sure that everything was ok during the visit? Maybe a mutual (non-alcholic) freind...or maybe a family member of the EX if your relationship with them is good?