Jeff,
You cannot convince a MOM with logic. "Logic be dammned, it's DANGEROUS!" is a typical, no possible response, discussion ender. There is a CHANCE something could happen. It isn't possible to remove all danger from backpacking. Or driving. Or crossing the street. Or…whatever. It won't matter. If she can reduce any danger by not having you go, that will be her first inclination. Given a choice, she will say no. Or give you one of those responses you listed ;-)
Just grit your teeth, tell her you are going, and when you will be back. Just an overnight somewhere for the first few times. Then a weekend…. You are a dad and a responsible one, else you would not even be asking about it. You are also an individual. If you need to get away, fine. Take her with you. Or, not. But do not let her tell you, you cannot. Rather, bolster her confidence in herself. She can handle it. She is a good mom. She can do it. She can, you know. Just make sure to do your "chores" before you leave. And, make sure to take the garbage out, do dishes as you clean the pack out and ask how she feels when you get back. Tell the child you missed him, bring back a toy…nicer if you made it. Spend some time with her, too. Not the MOM. Bring her a small gift, tell her you found it in a store and carried it for "x" miles on the trail, so you would not forget to give it to her (you wouldn't anyway…) Does she like hard to get candy? That one is easy… And that private stuff adults do.
Anyway, this stuff worked OK for me. She actually came when ours was a little under one year old. I changed to base camping and hiking down a canyon to do some fishing, instead. She had second kid in the basket, then. She actually found she liked it! The kid was occupied! The kids, as they grew, could get as dirty as they liked, and MOM didn't try to clean them every 5 minutes! They could play in the MUD and not have MOM tell them no. They can catch critters… and eat them… with MOM running over yelling to spit it out…ha ha… s u r e … nice and logical. ;-}
Well, this may be a bit of subversion. And it will take some plotting and scheming on your part. But, MOM is not logical, though you wife may be. You can tell her about it when you get back if she doesn't figure it out sooner.
My devious thoughts only . . .
jdm