Hi!...we are new to the site...
Why not spend the $ on the airfare to come up here to Alaskawith your whole family, stay in a little B&B cabin in the woods here near Seward; you can fish for salmon and halibut in the bay; fish for grayling, rainbows and dolly varden in the rivers; and purchase non-resident moose and black bear tags for $400/$225 respectivly. Our moose season is from Aug 20th-Sept 20th; b bear is never closed, and you don't need a guide for either, up here.
I'm not saying it's not work...but it's definitly do-able,especially talking with the right people. Their are several horseback hunting opportunities here on the Kenai Peninsula, too. Your dream and attitude are in the right place...keep up the good workouts, keep an open mind your options open.....and don't feel like your age is a setback. My man is 56 y/o and we are still active sheephunters. By the way, he would be impressed with your 500/600 yard shots you mentioned. He is a firm believer in honing that ability and having the confidence in taking the long shots: God knows that reality takes place more often than not at times up here....whether for sheep, or goat, or bear (our average shot distances are between 250-425 yards).A good knowledge and feel of your ballistics is integral to the success of the long shot, as you know.
Flying meat / fish on the plane, and mailing freezer boxes back home is pretty straight forward, and relativly inexpensive.....You could even donate some moose for a local family here in the area....(hint,hint)....