Thanks for all the suggestions.
We've done some PVC structure in the areas that kids bank fish from so they don't get hung up. We are planning more for this year. While the PVC won't rot, it does get pricey and time consuming when you look at large quantities.
The beauty of the trees for us is that we can send an email out to the whole neighborhood, and they will bring us about 150 trees, and drop the off at our community dock.
I'm exited to get them sunk, and see how things progress.
The amount of knowledge, and experience available here is incredible.
I'll post pictures of the sinking party, and see if I can get some good sonar pictures of the trees.