fly-fishing in Jackson Hole, Wyoming?

My mom and my grandfather are going on a trip to Jackson Hole. My grandfather is 83 and has always wanted to try fly-fishing. However, all the fly-fishing guides seem to charge a fortune--my mom couldn't find anything for less than $350 per person. They don't need a fancy tour--they just need someone who is an experienced angler to take them out for a couple of hours, do a demo, and let them try! It needs to be somewhere accessible for my grandfather who can't hike--he can walk slowly for short distances...they are New Yorkers--not experienced with the outdoors so they can't just rent equipment and go on their own. Anyideas??