We really need a bit more information. When in June? Early could have rivers running high, later is better. Is your grandson a proficient wader and flyfisher? How far from Boise are you willing to drive? How many days do you have allocated to fish?

As for guides, I'd call the local shops-- Idaho Anglers on Vista and Anglers on Overland. If you're looking to Eastern Oregon then contact Dave Tucker at:


http://www.dreamsonthefly.com/dave-tucker.html

One of the major rivers near Boise doesn't allow commercial guiding, plus it received a major burn and mudslides last fall/winter so it remains to see how it fared this summer, plus it is a river you'd float during June as it's somewhat difficult for beginners to access at its higher summer flows.

You may also want to consider the Sun Valley area as it has a lot of good water as well.

Sounds like you should have a lot of fun planning and executing this trip.