So, as a follow-up to my original question, a brief report on our experience for others who may ask the same question:
We did the ride last week and had a great time. The off-route gulf-coastal section, pretty much following US98 was partly good and partly not-so-good. We followed approximately this route: http://bit.ly/jhdGiy
The first day, on US98 from near Sopchoppy FL to near Mexico Beach (points A and B on the referenced map) was very pleasant and good not-busy roads with nice shoulders most of the way. We took 30A out to Indian Pass (near Port St. Joe), which was not unpleasant but hardly worth the extra miles; a thick pine forest is between the road and the water.
Between Mexico Beach and Miramar (points B and C, near Destin) was marginally unpleasant as it was lots of 4-lane roads, but with good shoulders and/or bike lanes. Panama City beach was super crowded and it was "Thunder Beach Weekend" ... 'nuff said. But, it was never unsafe, just kind of unpleasant on a bicycle.
From Miramar, it was much of the same until we crossed out to Santa Rosa island and got into the Gulf Shores National seashore, which was the whitest sand and bluest water I've ever seen, truly a wonderful ride through a wonderful place.
In Pensacola, we picked up the ACA route which was very nice, especially Dauphin Island, AL. We ended in Franklinton, LA, a little short of our intended endpoint, because of rear wheel issues with one of the bikes. In Franklinton, I highly recommend Mikes for ribs/steak and Louie's for cajun cooking.
Thanks, Jennifer for the help, and hope this helps someone.