I love all of your ideas and I have quite enjoyed reading your plans.
I am sure you have already read the pamphlet regarding tropical agriculture from ECHO, it showcases many of your aforementioned ideas.
I love that you plan on growing and using azolla. I, too, am a huge fan. The azolla that I grew extremely successfully in my pond was completely devastated by invading frogs. If i get azolla again ever, which I may because it was well-loved by my rabbits, I will keep a seed amount in reserve in case of predators again.
What I have switched over to in my ponds is water hyacinth, which is eaten fairly well by the rabbits, though they wont even consider eating the roots of it. It also grows extremely well here in West Florida and is not nearly as invasive as it is made out to be. Its also easy to harvest and carry to the rabbits and has an excellent protein rating. But you already knew that.
As on your planned property, roughage here is pretty easy to acquire. I too grow sugar cane, and deal with mineral poor soils. The seaweed idea is a great one. I may have to start doing that myself! I recently acquired some elephant grass, it seems to be as nutritious or perhaps moreso than corn, but I understand you may want the corn for its human/chicken value also. Have you considered sorghum or kefir? Both are grown quite a bit here, sorghum doubling as a molasses source. Not sure if that would be better than sugarcane at all, since its so easy to grow and the others would require planting regularly. But would certainly add to diversity.
I grow a lot of different types of gingers, which have roughage value for my rabbits and a great deal of edibilty and medicinal uses for humans. My favorites are cardamom ginger and shell ginger (Alpinia zerumbet), the latter of which is considered a superfood and called "Langkawas na pula" in its native Phillipines. Maybe your wife has heard of it! It thrives with no care and near full shade and would pair well with any banana ventures.
I also grow, eat, and feed to rabbits cannas, which taste great but are heavy feeders. These might be a pond edge plant which can grow a decent starchy tuber to compete with your cassavas. The tubers do need to be cooked first also, but lack the cyanide. Cannas also have a variety of beautiful flowers which may have cut value or potted plant resale value for your booth.
I cant wait to see pictures.