+1 to considering Idaho and browsing Adventure Cycling for ideas. I remember this article got me thinking about how touring needs to be different to be fun for kids but how everyone could benefit from those changes...
I toured most of the Katy several years ago. I think it can be a great first tour -- pleasantly off road with a very good trail surface and fun to do all or most of a trail in not too long a time commitment. The website is super helpful and fun to use for planning. And there were definitely some nicely scenic areas - especially the sections around Rocheport and McKittrick. I didn't find anything unsettling like indysteel, but I also was underwhelmed in that there are some really long sections with nothing but tree tunnel and sameness of not exciting scenery and agree that the town eating options were pretty dismal (keep in mind that I'm a veggie, like to eat healthy, AND we went in October when a lot was closed.)
The thing that surprised me, and was my knee's undoing (I stopped a day before the end in pain), was that the mileages were much harder than I thought they would be. Partially I undertrained for being the person who hauled the trailer, thinking that 40-60 miles a day with slower riders wouldn't be that hard. And the other thing was that the combination of the very steady grade and the limestone surface meant that you were ALWAYS pedaling. No coasting. Almost ever. It drove me a little nuts actually, and made me rethink the grand plan to tour all the rail trails in favor of doing more rolling hills and regular roads. I still want to do the GAP/C&O, and I still appreciate the traffic-free qualities and if riding with kids would prioritize them, but I would definitely revise daily mileage downward and put in more training with the equivalent load.
Great idea though -- I'm plotting to get my 16 year old nephew to tour with me next summer!
Sit bones = ~135 mm, saddles that work ~ 155cm/6.1 in wide
2003 da Vinci (custom road/all-rounder)/Terry Butterfly Ti
1994 Gary Fisher Nirvana (vintage MTB/commuter)/Terry Butterfly Chromoly
1991 Terry Symmetry (NOS frame/fork, project in progress)
1973 Raleigh Super Course (project in progress)