Your only three years older than I feel today after hauling and splitting fired wood for the past 4 days.
A good guide is going to put you as close to the caribou as he can. Yes the tundra is a bit rough at times but as we get older hopefully we hunt smarter. Up on the Seward Pen. we would park the plane and then get out the folding lounge chairs. The bou would walk right to the plane.
The main point is to not put yourself, unless in desperation, where you have to carry a caribou 2 miles. They wander all over the place but if you find an established trail and wait, they will come to you.
I don't know what outfitter you want to use but if the one I am using this fall works out well I will let everyone know. Ask the outfitters too. Don't be shy about your age, it isn't or should not be a handicap. I still cut and split my own wood. But like you stated, just a little slower.