I grew up in NB, and I probably won't take my kids on the Comal until they are teens. Growing up in the 80s and 90s it was the local's "family river" in large part because there were limited tube rentals and shuttles, but now you have to deal with a lot of the same trash that floats the Guadalupe, and the increased crowds, because it is so easy to get on the river.
Not being judgmental, I still like the river experience as much as I did 20+ years ago but don't want to subject my kids to it yet; we float the Frio with them instead.