IMHO, Take Him!
I can remember always being the kid who begged for someone to take me hunting and being told "No, you're not old enough" "wait till you get bigger". Since you asked for an opinion, here it is. I don't think five is an age that's ready for harvesting turkeys. The experience and memory of just being in the woods with dad should suffice for most kids. Consider getting a full blind for the two of you to sit in and call some birds in range. Let him see the birds come in and gobble. Just spending time out doors together is in my opinion more important than trying to rush him into "growing" up to fast. Besides it may not be legal for him to actually harvest a bird at five, for example here in Tennessee, ten years of age is the minimum age for a youth to purchase a license and harvest a bird and this is only after completing a hunter safety course, along with that a number of state's have mandates requiring a minimum of a 20 ga to be used for turkeys. Just don't rush things, carry him scouting, buy him a turkey call (past experience; kids love those gobble tubes that you shake) watch some tapes together even carry him in the evening to roost birds but I wouldn't put a gun in his hand just yet.. Good Luck in what ever you decide to do. The decision's yours.
Frog