Shimano makes wide ranging 7 speed freewheels. They're cheap and they work. I'm running one right now on my commuter. There is no particular reason to go to 9-10 speed for touring. You have a 126 mm drop out spacing and preferably you'd go to 135 mm (not 130) rear for touring (as that makes a stronger wheel) which means you really should have someone spread your frame who knows what he or she is doing. I'd leave it alone. People have toured successfully on 5-6-7-8-9-10. It just doesn't make that big a difference.