Mosey, There are special purpose adhesives made for concrete. They may be found at places like the big orange box (AKA Home Depot) or Lowe's. I think the pin and epoxy route has great merit too. If you fill the fracture line to overflowing and remove the excess, there won't be an opening or exposed porus entry point for moisture. If there is some chipping near the fracture line, after the epoxy or other glue cures well, you can use automotive body filler (Bondo) to fill in the missing places. After the Bondo starts to set up but before it gets really hard you can sand it, carve it with a knife, shape it with a SureForm (cheese grater rasp kinda thingy), or whatever.
How are you going to keep the drunks and other miscreants from shooting it during or near deer season? Seriously I would be concerned with where I placed something that someone with sufficiently impaired judgement to think it real would shoot at it and miss by a bit or MORE and hit the house or someother place that you don't want to take incoming rounds.
Patrick