It's best that you call the office to find out. They might not let you use your own if you are thinking of rafting down the river. However it's ok if you just want to float on the beach near the river. (Just be careful, the river is not deep but has strong current)
You should be able to drive down to the riverside campsites to drop off your tubes near the water, but as the other reply noted, you likely will only be permitted to float near the beach.
Thanks! Your answer is awaiting moderation.