Good news is the season opens on April 15, which this year falls on a Monday. That will eliminate some pressure. Bad news is it won't be all that much as the long wait to get in the turkey woods overrides everything else for most these days. The first week provides a lot more gobbling and seeing, but also a lot more frustration with people coming up on you, cutting off birds, shooting out of the roost, etc.
Generally toms are henned up the first week and into subsequent weeks depending on weather etc. Still good pressure through the second week, but down substantially. Birds that are easy to get to will be smarter, but if one is willing to get away from popular crowded areas near roads, one will find birds that probably haven't been messed with too much.
As you know being a long time turkey hunter, there is no perfect week. There are obviously better weeks. Based on getting your son's friend out here and having a quality experience for the boys, I think I would opt for starting on the weekend of the 27th and 28th and hunt through that next week and weekend ending on May 4th. That is unless you plan on spending more time. In that case extend it somewhat on either end.
You will see less pressure and birds will be plenty active. Many of the hens will probably be setting by then and gobblers won't be as henned up. Weather generally is pretty nice. You miss the early sometimes snowfalls and daytime temps are usually warmer. I know a guy that comes out every year from Georgia and he always chooses that time frame. Never a problem getting birds.
Best thing you can do irregardless is get to know where you want to go. Stevens and Ferry counties both have a lot of public lands...National Forest, WDFW, and BLM to a lesser extent along the reservoir. There are a good number of birds from down low to higher elevations. Most folks are hunting from the road, or not far from it. Stay away from those areas unless you they have been vacated.
Hope that helps. Lots of birds in the Northeast. You'll certainly hear and see them. Good luck. Make sure you post of some pictures when it all said and done.
