Great input, everyone, and I do appreciate it. Since I think I'm hooked, I view this 4-5 day trip this summer as a prelude to longer trips in the future ... call it a shake-down cruise, if you will. I plan to tack this 4-5 bike tour onto the beginning or end of a 4-5 day hiking trip in the White Mountains in NH. Since the far eastern leg of the Northern Tier route goes right through Conway, NH - about 10 miles from where I'll be staying - it seems like a natural fit.
I see this eventually morphing into 7-10 day trips (and maybe one day after I retire, a cross-country trip) so I'm considering buying gear now that I can use in the future, too. That said, I suppose If I get that serious about bike touring I'll probably get serious about buying a more suitable touring bike. But in the meantime, I need to make do with what I can use or adapt for my existing bike. I'd like to buy good stuff now and be able to use it indefinitely.
So far, the Tubus Smarti looks like it could work.